In this paper, traffic accidents on the road section contain a tunnel were analyzed based on 406 traffic accidents data. The analyzed data were prepared by extracting a part of accident data base stored by Yamaguchi Prefecture Police Department during 1996-1997 and 1999-2003. The length of investigated road section was 1400 m and included a tunnel of 550 m. After accidents on the road section were pigeonhole, several factors were selected and those influence on traffic accidents were investigated in detail.