A sleepiness level prediction device includes a vehicle information acquisition unit, a driver information acquisition unit, and a control unit. The vehicle information acquisition unit is configured to acquire information relating to a vehicle. The driver information acquisition unit is configured to acquire information relating to a driver. The control unit is configured to calculate a stimulus amount to be given to the driver based on a current driving load of the driver and a driving load after a prescribed time, based on the information relating to the vehicle, calculate a non-acclimation degree indicative of a level at which the driver is not acclimated to driving based on a change in the stimulus amount, and predict a sleepiness level of the driver after the prescribed time based on a current sleepiness level of the driver estimated based on the information relating to the driver and the non-acclimation degree.
Sleepiness level prediction device and sleepiness level prediction method