An arousal-level determining apparatus includes a generating unit, a calculating unit, an identifying unit, and a determining unit. The generating unit generates heartbeat-interval variation data, which indicates changes in heartbeat interval, on the basis of heartbeat signals indicating subjects heartbeats. The calculating unit 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 identifies a feature point corresponding to a spectral density peak in the calculated spectral densities in the frequency bands. The determining unit determines subjects arousal level on the basis of the identified feature point.
