A vehicle-mounted apparatus that is capable of wireless connection with a roadside device which is on, above, or below a road, the vehicle-mounted apparatus being on a vehicle, the vehicle-mounted apparatus comprising: storage; and processing circuitry that, in operation, performs operations including: acquiring position information that is broadcast from the roadside device by wireless communication, the position information being about a position of the roadside device; characterized by acquiring range information that is broadcast from the roadside device by the wireless communication, the range information being about a detection range of a sensor of the roadside device; deciding whether individual wireless connection is to be performed between the roadside device and the vehicle-mounted apparatus based on roadside device information, the roadside device information including the position information about the position of the roadside device and the range information about the detection range of the roadside device, wherein it is decided to perform the individual wireless connection between the roadside device and the vehicle-mounted apparatus when the roadside device is positioned within a prescribed distance from a planned traveling route of the vehicle or when the roadside device is positioned within a prescribed distance from the vehicle or when the detection range includes the planned traveling route of the vehicle; connecting or disconnecting the individual wireless connection between the vehicle-mounted apparatus and the roadside device based on the deciding; and acquiring periphery information of the roadside device from the roadside device during the individual wireless connection between the vehicle-mounted apparatus and the roadside device in response to the individual wireless connection being connected. storage; and processing circuitry that, in operation, performs operations including: acquiring position information that is broadcast from the roadside device by wireless communication, the position information being about a position of the roadside device; characterized by acquiring range information that is broadcast from the roadside device by the wireless communication, the range information being about a detection range of a sensor of the roadside device; deciding whether individual wireless connection is to be performed between the roadside device and the vehicle-mounted apparatus based on roadside device information, the roadside device information including the position information about the position of the roadside device and the range information about the detection range of the roadside device, wherein it is decided to perform the individual wireless connection between the roadside device and the vehicle-mounted apparatus when the roadside device is positioned within a prescribed distance from a planned traveling route of the vehicle or when the roadside device is positioned within a prescribed distance from the vehicle or when the detection range includes the planned traveling route of the vehicle; connecting or disconnecting the individual wireless connection between the vehicle-mounted apparatus and the roadside device based on the deciding; and acquiring periphery information of the roadside device from the roadside device during the individual wireless connection between the vehicle-mounted apparatus and the roadside device in response to the individual wireless connection being connected. acquiring position information that is broadcast from the roadside device by wireless communication, the position information being about a position of the roadside device; characterized by acquiring range information that is broadcast from the roadside device by the wireless communication, the range information being about a detection range of a sensor of the roadside device; deciding whether individual wireless connection is to be performed between the roadside device and the vehicle-mounted apparatus based on roadside device information, the roadside device information including the position information about the position of the roadside device and the range information about the detection range of the roadside device, wherein it is decided to perform the individual wireless connection between the roadside device and the vehicle-mounted apparatus when the roadside device is positioned within a prescribed distance from a planned traveling route of the vehicle or when the roadside device is positioned within a prescribed distance from the vehicle or when the detection range includes the planned traveling route of the vehicle; connecting or disconnecting the individual wireless connection between the vehicle-mounted apparatus and the roadside device based on the deciding; and acquiring periphery information of the roadside device from the roadside device during the individual wireless connection between the vehicle-mounted apparatus and the roadside device in response to the individual wireless connection being connected.