In the study, the earthquake records of Aratozawa Dam during the past 24 years are analyzed. It was pointed out that, struck by the Iwate-Miyagi Nairiku Earthquake in 2008, the fundamental frequencies and acceleration amplification ratios of the dam fell temporarily, and they recovered a few days after this earthquake. Furthermore, cross spectra and coherence functions of the earthquake records are analyzed to investigate the correlation of earthquake response of the dam crest with the seismic motions of the lower bedrock and those of both banks. It has been found that in the lower frequency domain up to the fundamental frequency of the dam body, the seismic motion of the lower bedrock contributes greatly to the response of the dam body, and in the higher frequency domain the contribution of both banks predominates over that of the lower bedrock.