A parking assistance device according to an embodiment includes a determination unit that determines, when the parallel parking of a vehicle in a parking area is assisted, whether the parking space length of a frontage that the vehicle enters in the parking area is the sum of the full length of the vehicle and a certain length or more and a control unit that performs parking assistance for the vehicle along a route in which stationary steering control is not performed at a turning position of the vehicle when the parking space length is the sum of the full length of the vehicle and the certain length or more.