PURPOSE: To surely identify a vehicle even in a situation where the image pickup of a number plate with a television camera is difficult.

CONSTITUTION: Resonance circuits R1 to Rn having mutually different resonance frequency bands are stuck to the rear face of a number plate 10 fixed to a vehicle. The combination of the resonance frequency bands corresponds to a registered number formed on the surface of the number plate 10. A road side device 6 arranged on a road is provided with are oscillation circuit 11. The resonance circuits R1 to Rn are excited by a radio wave generated from the circuit 11 and radio waves having respective resonance frequency bands are generated. These radio waves are received by a receiving part 12. The frequency bands of radio waves received by the receiving part 12 are idendified by a frequency identification part 13. A vehicle identification part 14 recognizes the registered number of the vehicle based upon the identified result and outputs vehicle number information.