DRIVING ASSISTANCE DEVICE

A driving assistance device of the embodiment includes: an acquisition unit that acquires a degree of drowsiness of a driver who is driving a vehicle, based on information on the driver being input; a calculation unit that calculates an expected time until the effect is lost indicating an expected time when drowsiness is not eliminated despite a stimulus being applied to the driver, based on a time interval when the degree of drowsiness obtained by the acquisition unit becomes equal to or more than a predetermined threshold; and a control unit that changes control performed on the driver as the expected time until the effect is lost calculated by the calculation unit is reduced.