To provide an assist device capable of facilitating loading/unloading of luggage into a luggage compartment of a vehicle.

During stopping or parking of the vehicle, a controller 1 unlocks a back door 70a based on a request of unlocking the back door 70a(S10-S20) and determines whether a request for operating an assist tool 90a exists or not (S13). When the request for operation exists, under a condition that there is no obstacle around the back door 70a and around the assist tool 90a (S14), the controller prohibits travelling of the vehicle (S15), opens the back door 70a (S16, S17), and drives the assist tool 90a (S18).