diff --git a/kadai1/ramenjuniti/Makefile b/kadai1/ramenjuniti/Makefile
new file mode 100644
index 0000000..55e5687
--- /dev/null
+++ b/kadai1/ramenjuniti/Makefile
@@ -0,0 +1,14 @@
+BIN := iconv
+
+.PHONY: test
+test:
+	go test -cover -v ./...
+
+.PHONY: build
+build: test
+	go build -o $(BIN)
+
+.PHONY: clean
+clean:
+	rm $(BIN)
+	go clean
diff --git a/kadai1/ramenjuniti/README.md b/kadai1/ramenjuniti/README.md
new file mode 100644
index 0000000..8d20082
--- /dev/null
+++ b/kadai1/ramenjuniti/README.md
@@ -0,0 +1,31 @@
+# iconv
+
+## Description
+
+課題１（画像変換コマンドを作ろう）を実装したもの
+
+以下のパッケージで構成されています
+
+- main
+- target
+- imgconv
+
+## Usage
+
+```
+iconv -in {変換前の形式} -out {変換したい形式} {ディレクトリ}
+```
+
+jpg, png, gif, tif, bmp に対応しています
+
+## Build
+
+```bash
+make build
+```
+
+## Test
+
+```bash
+make test
+```
diff --git a/kadai1/ramenjuniti/go.mod b/kadai1/ramenjuniti/go.mod
new file mode 100644
index 0000000..64730b3
--- /dev/null
+++ b/kadai1/ramenjuniti/go.mod
@@ -0,0 +1,5 @@
+module github.com/gopherdojo/dojo5/kadai1/ramenjuniti
+
+go 1.12
+
+require golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff
diff --git a/kadai1/ramenjuniti/go.sum b/kadai1/ramenjuniti/go.sum
new file mode 100644
index 0000000..e1df7c3
--- /dev/null
+++ b/kadai1/ramenjuniti/go.sum
@@ -0,0 +1,3 @@
+golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff h1:+2zgJKVDVAz/BWSsuniCmU1kLCjL88Z8/kv39xCI9NQ=
+golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
diff --git a/kadai1/ramenjuniti/imgconv/imgconv.go b/kadai1/ramenjuniti/imgconv/imgconv.go
new file mode 100644
index 0000000..5666f6d
--- /dev/null
+++ b/kadai1/ramenjuniti/imgconv/imgconv.go
@@ -0,0 +1,69 @@
+package imgconv
+
+import (
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+	"os"
+	"path/filepath"
+
+	"golang.org/x/image/bmp"
+	"golang.org/x/image/tiff"
+)
+
+// ImgData デコードされた画像データが入る
+type ImgData struct {
+	Path string
+	Data image.Image
+}
+
+// Decode pathの画像をデコードし、ImgDataに入れる
+func Decode(path string) (*ImgData, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	img, _, err := image.Decode(file)
+	if err != nil {
+		return nil, err
+	}
+
+	return &ImgData{Path: path, Data: img}, nil
+}
+
+// Encode iのDataをout形式のファイルにエンコードし、ファイル作成
+// jpg, png, gif, tif, bmpに対応
+func (i *ImgData) Encode(out string) error {
+	file, err := os.Create(rmExt(i.Path) + "." + out)
+	if err != nil {
+		return err
+	}
+
+	switch out {
+	case "png":
+		err = png.Encode(file, i.Data)
+	case "jpg", "jpeg":
+		err = jpeg.Encode(file, i.Data, nil)
+	case "gif":
+		err = gif.Encode(file, i.Data, nil)
+	case "tif", "tiff":
+		err = tiff.Encode(file, i.Data, nil)
+	case "bmp":
+		err = bmp.Encode(file, i.Data)
+	}
+
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	return nil
+}
+
+// rmExt pathの拡張子を除いた文字列を返す
+func rmExt(path string) string {
+	return path[:len(path)-len(filepath.Ext(path))]
+}
diff --git a/kadai1/ramenjuniti/imgconv/imgconv_test.go b/kadai1/ramenjuniti/imgconv/imgconv_test.go
new file mode 100644
index 0000000..ae74da0
--- /dev/null
+++ b/kadai1/ramenjuniti/imgconv/imgconv_test.go
@@ -0,0 +1,64 @@
+package imgconv
+
+import (
+	"os"
+	"testing"
+)
+
+var tests = []struct {
+	name    string
+	path    string
+	out     string
+	outFile string
+}{
+	{
+		name:    "jpg to png",
+		path:    "../testdata/imgconv/sample.jpg",
+		out:     "png",
+		outFile: "../testdata/imgconv/sample.png",
+	},
+	{
+		name:    "jpg to gif",
+		path:    "../testdata/imgconv/sample.jpg",
+		out:     "gif",
+		outFile: "../testdata/imgconv/sample.gif",
+	},
+	{
+		name:    "jpg to tif",
+		path:    "../testdata/imgconv/sample.jpg",
+		out:     "tif",
+		outFile: "../testdata/imgconv/sample.tif",
+	},
+	{
+		name:    "jpg to bmp",
+		path:    "../testdata/imgconv/sample.jpg",
+		out:     "bmp",
+		outFile: "../testdata/imgconv/sample.bmp",
+	},
+}
+
+func TestConvert(t *testing.T) {
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			img, err := Decode(test.path)
+			if err != nil {
+				t.Fatalf("unexpected error %v", err)
+			}
+
+			err = img.Encode(test.out)
+			if err != nil {
+				t.Fatalf("unexpected error %v", err)
+			}
+
+			_, err = os.Stat(test.outFile)
+			if err != nil {
+				t.Fatalf("did not create %v", test.outFile)
+			}
+
+			err = os.Remove(test.outFile)
+			if err != nil {
+				t.Fatalf("cannot remove %v", test.outFile)
+			}
+		})
+	}
+}
diff --git a/kadai1/ramenjuniti/main.go b/kadai1/ramenjuniti/main.go
new file mode 100644
index 0000000..d2c9c48
--- /dev/null
+++ b/kadai1/ramenjuniti/main.go
@@ -0,0 +1,71 @@
+package main
+
+import (
+	"flag"
+	"log"
+
+	"github.com/gopherdojo/dojo5/kadai1/ramenjuniti/imgconv"
+	"github.com/gopherdojo/dojo5/kadai1/ramenjuniti/target"
+)
+
+func main() {
+	in := flag.String("in", "jpg", "file type before conversion")
+	out := flag.String("out", "png", "file type to convert")
+	formats := []string{"jpg", "png", "gif", "tif", "bmp"}
+
+	flag.Parse()
+	args := flag.Args()
+
+	if len(args) == 0 {
+		log.Fatal("directory not specified")
+	}
+
+	if *in == "jpeg" {
+		*in = "jpg"
+	}
+	if *in == "tiff" {
+		*in = "tif"
+	}
+	if *out == "jpeg" {
+		*out = "jpg"
+	}
+	if *out == "tiff" {
+		*out = "tif"
+	}
+
+	if !canConv(*in, formats) {
+		log.Fatalf("cannot convert %v file", *in)
+	}
+	if !canConv(*out, formats) {
+		log.Fatalf("cannot convert %v file", *out)
+	}
+
+	for _, arg := range args {
+		targets, err := target.Get(arg, *in)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		for _, t := range targets {
+			img, err := imgconv.Decode(t)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			err = img.Encode(*out)
+			if err != nil {
+				log.Fatal(err)
+			}
+		}
+	}
+}
+
+// canConv tがconvに含まれるかどうかをboolで返す
+func canConv(f string, formats []string) bool {
+	for _, v := range formats {
+		if f == v {
+			return true
+		}
+	}
+	return false
+}
diff --git a/kadai1/ramenjuniti/target/target.go b/kadai1/ramenjuniti/target/target.go
new file mode 100644
index 0000000..8c480eb
--- /dev/null
+++ b/kadai1/ramenjuniti/target/target.go
@@ -0,0 +1,25 @@
+package target
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// Get root下のin形式のファイルのパスが入ったsliceとerrを返す
+func Get(root, in string) ([]string, error) {
+	targets := []string{}
+
+	err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
+		if filepath.Ext(path) == "."+in {
+			targets = append(targets, path)
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return targets, err
+	}
+
+	return targets, nil
+}
diff --git a/kadai1/ramenjuniti/target/target_test.go b/kadai1/ramenjuniti/target/target_test.go
new file mode 100644
index 0000000..1231a1b
--- /dev/null
+++ b/kadai1/ramenjuniti/target/target_test.go
@@ -0,0 +1,84 @@
+package target
+
+import (
+	"reflect"
+	"testing"
+)
+
+var tests = []struct {
+	name    string
+	root    string
+	in      string
+	targets []string
+}{
+	{
+		name: "get jpg files",
+		root: "../testdata/target",
+		in:   "jpg",
+		targets: []string{
+			"../testdata/target/jpg/sample1.jpg",
+			"../testdata/target/jpg/sample2.jpg",
+			"../testdata/target/jpg/sample3.jpg",
+		},
+	},
+	{
+		name: "get png files",
+		root: "../testdata/target",
+		in:   "png",
+		targets: []string{
+			"../testdata/target/png/sample1.png",
+			"../testdata/target/png/sample2.png",
+			"../testdata/target/png/sample3.png",
+		},
+	},
+	{
+		name: "get gif files",
+		root: "../testdata/target",
+		in:   "gif",
+		targets: []string{
+			"../testdata/target/gif/sample1.gif",
+			"../testdata/target/gif/sample2.gif",
+			"../testdata/target/gif/sample3.gif",
+		},
+	},
+	{
+		name: "get tif files",
+		root: "../testdata/target",
+		in:   "tif",
+		targets: []string{
+			"../testdata/target/tif/sample1.tif",
+			"../testdata/target/tif/sample2.tif",
+			"../testdata/target/tif/sample3.tif",
+		},
+	},
+	{
+		name: "get bmp files",
+		root: "../testdata/target",
+		in:   "bmp",
+		targets: []string{
+			"../testdata/target/bmp/sample1.bmp",
+			"../testdata/target/bmp/sample2.bmp",
+			"../testdata/target/bmp/sample3.bmp",
+		},
+	},
+	{
+		name:    "no file",
+		root:    "../testdata/target",
+		in:      "hoge",
+		targets: []string{},
+	},
+}
+
+func TestGet(t *testing.T) {
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := Get(test.root, test.in)
+			if err != nil {
+				t.Fatalf("unexpected error %v", err)
+			}
+			if !reflect.DeepEqual(got, test.targets) {
+				t.Fatalf("got targets: %v, want targets: %v", got, test.targets)
+			}
+		})
+	}
+}
diff --git a/kadai1/ramenjuniti/testdata/imgconv/sample.jpg b/kadai1/ramenjuniti/testdata/imgconv/sample.jpg
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