Provided are an alertness device configured such that a load is low in the processing for alertness determination and that the accuracy in alertness determination is high, a seat including the alertness device, and an alertness determination method. The al...

A sleepiness assessment value P1 is set to be an average heart rate HR (S130). A sleepiness assessment value P2 is set to be a standard deviation à of a respiration interval RespI for one minute (S150). A sleepiness assessment value P3 is set to be a valu...