In the parking assistance device, the comparison unit 130 configured to compare the parking priority of the first vehicle 21 and the second vehicle 22-provided, however, that the first vehicle is a vehicle to be newly parked in a parking compartment And the second vehicle is a vehicle capable of automatically driving already parked in the first parking space; When the parking priority related to the use of the first parking space of the first vehicle is higher than the parking priority related to the use of the first parking space of the second vehicle, the second vehicle A first indicating unit 140 configured to output a signal instructing to leave the parking space by automatic driving; When the parking priority for use of the first parking space of the first vehicle is higher than the parking priority for use of the first parking space of the second vehicle, for the first vehicle, the And a second instruction unit 150 configured to output a signal instructing to park in the first parking space.