When it has been assessed by an assessment unit (5) that among wireless communication terminals (8a - 8d) a wireless communication terminal (8a) has been left behind in a vehicle passenger compartment, a control unit (6) selects a wireless communication protocol from among a plurality of different wireless communication protocols according to the degree of separation of the wireless communicationterminals (8b - 8d) from the vehicle. A wireless communication unit (2), which is capable of switching wireless communication among each of the plurality of wireless communication protocols, transmitsleft behind notification information, via the wireless communication with the wireless communication protocol which has been selected by the control unit (6), to the wireless communication terminal which is outside of the vehicle passenger compartment.