diff --git a/amazon_transcribe_handler.go b/amazon_transcribe_handler.go
index 705b15b..fe6866c 100644
--- a/amazon_transcribe_handler.go
+++ b/amazon_transcribe_handler.go
@@ -103,9 +103,12 @@ func (h *AmazonTranscribeHandler) Handle(ctx context.Context, reader io.Reader)
 				case *transcribestreamingservice.TranscriptEvent:
 					if h.OnResultFunc != nil {
 						if err := h.OnResultFunc(ctx, w, h.ChannelID, h.ConnectionID, h.LanguageCode, e.Transcript.Results); err != nil {
-							errResponse := NewSuzuErrorResponse(err.Error())
-							if err := encoder.Encode(errResponse); err != nil {
-								// TODO: ログを書く
+							if err := encoder.Encode(NewSuzuErrorResponse(err.Error())); err != nil {
+								zlog.Error().
+									Err(err).
+									Str("channel_id", h.ChannelID).
+									Str("connection_id", h.ConnectionID).
+									Send()
 							}
 							w.CloseWithError(err)
 							return
diff --git a/speech_to_text_handler.go b/speech_to_text_handler.go
index 7fbe192..5681390 100644
--- a/speech_to_text_handler.go
+++ b/speech_to_text_handler.go
@@ -144,9 +144,12 @@ func (h *SpeechToTextHandler) Handle(ctx context.Context, reader io.Reader) (*io
 
 			if h.OnResultFunc != nil {
 				if err := h.OnResultFunc(ctx, w, h.ChannelID, h.ConnectionID, h.LanguageCode, resp.Results); err != nil {
-					errResponse := NewSuzuErrorResponse(err.Error())
-					if err := encoder.Encode(errResponse); err != nil {
-						// TODO: ログを書く
+					if err := encoder.Encode(NewSuzuErrorResponse(err.Error())); err != nil {
+						zlog.Error().
+							Err(err).
+							Str("channel_id", h.ChannelID).
+							Str("connection_id", h.ConnectionID).
+							Send()
 					}
 					w.CloseWithError(err)
 					return
diff --git a/test_handler.go b/test_handler.go
index 4b143fe..15fc137 100644
--- a/test_handler.go
+++ b/test_handler.go
@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+
+	zlog "github.com/rs/zerolog/log"
 )
 
 func init() {
@@ -61,9 +63,12 @@ func (h *TestHandler) Handle(ctx context.Context, reader io.Reader) (*io.PipeRea
 			n, err := reader.Read(buf)
 			if err != nil {
 				if err != io.EOF {
-					errResponse := NewSuzuErrorResponse(err.Error())
-					if err := encoder.Encode(errResponse); err != nil {
-						// TODO: ログを書く
+					if err := encoder.Encode(NewSuzuErrorResponse(err.Error())); err != nil {
+						zlog.Error().
+							Err(err).
+							Str("channel_id", h.ChannelID).
+							Str("connection_id", h.ConnectionID).
+							Send()
 					}
 				}
 				w.CloseWithError(err)
@@ -77,9 +82,12 @@ func (h *TestHandler) Handle(ctx context.Context, reader io.Reader) (*io.PipeRea
 
 				if h.OnResultFunc != nil {
 					if err := h.OnResultFunc(ctx, w, h.ChannelID, h.ConnectionID, h.LanguageCode, result); err != nil {
-						errResponse := NewSuzuErrorResponse(err.Error())
-						if err := encoder.Encode(errResponse); err != nil {
-							// TODO: ログを書く
+						if err := encoder.Encode(NewSuzuErrorResponse(err.Error())); err != nil {
+							zlog.Error().
+								Err(err).
+								Str("channel_id", h.ChannelID).
+								Str("connection_id", h.ConnectionID).
+								Send()
 						}
 						w.CloseWithError(err)
 						return