diff --git a/app/services/attendance_statistics_service.rb b/app/services/attendance_statistics_service.rb
index e31049b22..4e3a18ae9 100644
--- a/app/services/attendance_statistics_service.rb
+++ b/app/services/attendance_statistics_service.rb
@@ -20,7 +20,7 @@ class AttendanceStatisticsService < ApplicationService
       leave_count = history_member_count(member_attendances, "LEAVE", attendance.id)
       all_count = member_attendances.select{|member_attendance| member_attendance.course_attendance_id == attendance.id}.size
 
-      normal_rate = cal_rate(normal_count, all_count)
+      normal_rate = all_count == 0 ? 1 : cal_rate(normal_count, all_count)
       all_normal_rate << normal_rate
       absence_rate = cal_rate(absence_count, all_count)
       all_absence_rate << absence_rate