This study was conducted to clarify the relationship between forest understory habitat and small rodents in the study sites of 500m, 800m and 1,100m a. s. l. of 6 areas in Mt. Chirisan National Park from July 1997 to August 1998. Coverage of understory vegetation and depth of litter layer were increased as the increase of altitude. Seventy seven individuals of Apodemus agrarius, A. peninsulae and Eothenomys regulus were captured in all study areas. There were significantly correlations among coverage of understory vegetation, depth of litter layer and number of captured small rodents. Increase of understory vegetation coverage and litter layer would provide the proper habitat condition for small rodents.