A vehicle-mounted apparatus that is capable of wireless connection with a roadside device is provided. The roadside device is on, above, or below a road. The vehicle-mounted apparatus is on a vehicle and acquires position information broadcast from the roadside device by wireless communication. The position information is about a position of the roadside device. The vehicle-mounted apparatus decides whether individual wireless connection is performed between the roadside device and the vehicle-mounted apparatus based on roadside device information. The roadside device information includes the position information about the position of the roadside device. Connection or disconnection of individual wireless connection is performed between the vehicle-mounted apparatus and the roadside device based on the decision. Periphery information of the roadside device is acquired from the roadside device during the individual wireless connection in response to the individual wireless connection being connected.