A sleepiness level detection device detects a heartbeat signal when a time equal to or longer than T 1 and equal to or shorter than T 2 has elapsed since the start of driving. The heartbeat signal is subjected to FFT processing to obtain a spectrum signal. By use of a peak frequency of the spectrum signal, a driver conscious-state peak frequency is estimated. A consciousness level index band alpha is set with respect to the conscious-state peak frequency. A sleepiness level index band beta is set with respect to a frequency, which is calculated by multiplying the conscious-state peak frequency by a predetermined ratio (65 to 90%). A sleepiness level evaluation parameter Sp (=betap/(alphap+betap)) for indicating the sleepiness level of the driver is calculated with the use of the strength alphap and betap of spectrum signals.
Sleepiness level detection device