A sleepiness-estimating device capable of improving the precision of sleepiness estimation by eliminating the effect of individual differences. In the device, a recurrence time-calculating part (103) calculates the recurrence time, which is the time needed, after a detection time when an action is detected, for a sleepiness estimation parameter value acquired after the detection time to return to the value of the sleepiness estimation parameter acquired before the detection time. A sleepiness-estimating part (104) estimates the level of sleepiness of the sleepiness-estimation subject on the basis of the calculated recurrence time. To be specific, the sleepiness-estimating part (104) maintains a sleepiness level-estimating table in which each of multiple time ranges is correlated with a possible sleepiness level, and specifies a possible sleepiness level that corresponds to the time range, among the multiple time ranges, with which the recurrence time is associated.
SLEEPINESS-ESTIMATING DEVICE AND SLEEPINESS-ESTIMATING METHOD