When performing automatic control of a steering device (2) that assists a host vehicle to be pulled into or out of a parking space, an electronic control unit (9) performs the following procedure. When there is, as a path for pulling the vehicle into or out of the parking space, a path in which a predicted temperature Tf of the steering device (2) for when the automatic control is performed to move the vehicle along the path would be lower than an allowable upper limit value Tm, the electronic control unit (9) starts the automatic control to move the vehicle along the path. In contrast, when there is no path in which the predicted temperature Tf is lower than the allowable upper limit value Tm, the electronic control unit (9) prohibits the automatic control.