An arousal-level determining apparatus (100) includes a generating unit (120), a calculating unit (130), an identifying unit (140), and a determining unit (180). The generating unit (120) generates heartbeat-interval variation data, which indicates changes in heartbeat interval, on the basis of heartbeat signals indicating subject's heartbeats. The calculating unit (130) applies a band-pass filter, which allows passage of a certain range of frequencies, to each frequency band in the heartbeat-interval variation data while changing the frequency band, and calculates spectral density with respect to each frequency band applied with the band-pass filter. The identifying unit (140) identifies a feature point corresponding to a spectral density peak in the calculated spectral densities in the frequency bands. The determining unit (180) determines subject's arousal level on the basis of the identified feature point.
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