In a system, a parallel-parking number that is the number of the parking spaces aligned in the parallel-parking direction is acquired for each parking area. A vacancy number that is the number of vacant parking spaces is acquired for each parking area. Based on the parallel-parking number, a vacancy number threshold value is calculated that is a threshold value of the vacancy number for calculating a priority of each parking area, in one of which an automated-parking-target vehicle is to be parked. The priorities are calculated such that the priority of a parking area with the vacancy number equal to or larger than the vacancy number threshold value is higher than the priority of a parking area with the vacancy number smaller than the vacancy number threshold value. The automated-parking-target vehicle is caused to park preferentially in a parking space in the parking area with the higher priority.