During the Iwate-Miyagi Nairiku Earthquake (M7.2) of June 14, 2008, earthquake motions with the maximum acceleration of 1,024 cm/sec2 in the stream direction was recorded at the foundation bedrock of Aratozawa Dam located approximately 16 km from the epicenter. The maximum response acceleration in the same direction near the center of the dam crest was 525 cm/sec2, and the acceleration amplification ratio of the dam body was far lower than that normally considered for a rockfill dam. This study identified the dynamical properties of Aratozawa Dam and then analytically reproduced the recorded earthquake behavior of the dam body. The generating mechanism of the peculiar earthquake behavior was investigated based on the results of earthquake response analysis of the dam body. Furthermore, the residual deformation of the dam body was considered to be caused by the shaking compressive subsidence based on sliding stability and cumulative damage analyses.