When the entry or exit of a vehicle with respect to a parking space is assisted through an automatic control of a steering device (2), the amount of temperature rise of a motor (2a) of the steering device (2) through the execution of the automatic control is calculated such that the larger the margin (margin length) of the dimension of the parking space relative to the size of the vehicle, the greater the amount of temperature rise becomes. The amount of temperature rise is added to the current value of the temperature of the motor (2a) to calculate the predicted temperature of the motor (2a) subjected to a temperature rise through the execution of the automatic control. When the predicted temperature is equal to or higher than a determination value, the execution of the automatic control is inhibited. In contrast, the execution is permitted when the predicted temperature is lower than the determination value.