diff --git a/go.mod b/go.mod
index 7cc2f2f..ee04e22 100644
--- a/go.mod
+++ b/go.mod
@@ -6,6 +6,7 @@ require (
 	github.com/d5/tengo/v2 v2.6.2
 	github.com/google/go-cmp v0.5.2
 	github.com/sirupsen/logrus v1.7.0
+	github.com/suzuki-shunsuke/go-convmap v0.1.0
 	github.com/suzuki-shunsuke/go-findconfig v0.1.0
 	github.com/urfave/cli/v2 v2.2.0
 	gopkg.in/yaml.v2 v2.3.0
diff --git a/go.sum b/go.sum
index f125b01..3399238 100644
--- a/go.sum
+++ b/go.sum
@@ -15,6 +15,8 @@ github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeV
 github.com/sirupsen/logrus v1.7.0 h1:ShrD1U9pZB12TX0cVy0DtePoCH97K8EtX+mg7ZARUtM=
 github.com/sirupsen/logrus v1.7.0/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/suzuki-shunsuke/go-convmap v0.1.0 h1:0qzSC9IAzYdylNJvgzFpxbD/KeWpuVM608d/S0VjYsU=
+github.com/suzuki-shunsuke/go-convmap v0.1.0/go.mod h1:S0yDqBPFU0lmlHhoMKNSSHDRt87tUyI+KY/fBuXNn14=
 github.com/suzuki-shunsuke/go-findconfig v0.1.0 h1:ORAMPULNwus1kIvhcHaubo0Pw1ehlgRbSAxmAJL7KI4=
 github.com/suzuki-shunsuke/go-findconfig v0.1.0/go.mod h1:u/0Zz6/GDE6G0gofzVhR9UPOIKLSUoDMjUoFWqOoVlg=
 github.com/urfave/cli v1.22.4 h1:u7tSpNPPswAFymm8IehJhy4uJMlUuU/GmqSkvJ1InXA=
diff --git a/pkg/config/config.go b/pkg/config/config.go
index 910ccb7..c210dbb 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -2,6 +2,8 @@ package config
 
 import (
 	"fmt"
+
+	"github.com/suzuki-shunsuke/go-convmap/convmap"
 )
 
 type Config struct {
@@ -29,14 +31,14 @@ type Test struct {
 func ConvertConfig(cfg Config) error {
 	for i, entry := range cfg.Entries {
 		for k, v := range entry.Params {
-			p, err := ConvertMapKey(v)
+			p, err := convmap.Convert(v)
 			if err != nil {
 				return fmt.Errorf("convert entry.params: entry_name: %s: key: %s: %w", entry.Name, k, err)
 			}
 			entry.Params[k] = p
 		}
 		for j, test := range entry.Tests {
-			p, err := ConvertMapKey(test.Equal)
+			p, err := convmap.Convert(test.Equal)
 			if err != nil {
 				return fmt.Errorf("convert test.Equal: entry_name: %s: test_name: %s: %w", entry.Name, test.Name, err)
 			}
@@ -47,33 +49,3 @@ func ConvertConfig(cfg Config) error {
 	}
 	return nil
 }
-
-func ConvertMapKey(data interface{}) (interface{}, error) {
-	switch t := data.(type) {
-	case map[interface{}]interface{}:
-		m := make(map[string]interface{}, len(t))
-		for k, v := range t {
-			s, ok := k.(string)
-			if !ok {
-				return nil, fmt.Errorf("the map key should be string: %+v", k)
-			}
-			val, err := ConvertMapKey(v)
-			if err != nil {
-				return nil, fmt.Errorf("key: %s: %w", s, err)
-			}
-			m[s] = val
-		}
-		return m, nil
-	case []interface{}:
-		for i, v := range t {
-			val, err := ConvertMapKey(v)
-			if err != nil {
-				return nil, fmt.Errorf("index: %d: %w", i, err)
-			}
-			t[i] = val
-		}
-		return t, nil
-	default:
-		return data, nil
-	}
-}