A fatigue reducing device according to an embodiment includes, as an example, a determinator that determines whether an occupant sitting on a seat of a vehicle is driving the vehicle, and a controller that controls a vibration device provided in the seat to apply vibration stimulation at a first frequency causing muscular tension to a second muscle serving that is an antagonist muscle to a first muscle that is a massage target in a case where the determinator has determined that the occupant is driving the vehicle.
