A controller of a first vehicle specifies a position of an unoccupied parking space, from a detected position of the first vehicle and an image shot with a camera. A server-side controller transmits target parking space information indicating a position of a parking space within a predetermined range from a position of a second vehicle which has transmitted a request, of the positions of the parking spaces indicated by vacant parking space information from the first vehicle, to the second vehicle. A controller of the second vehicle obtains the target parking space information from the server. An informer of the second vehicle informs the position of the parking space indicated by the obtained target parking space information.