A stationary device 20 sends a portable-device finding signal to a portable device 10 from a plurality of stationary-device side antennae 24 and 25, which are located at different positions. Upon receipt of the portable-device finding signal from the stationary device 20, the portable device 10 sends a reception intensity data signal to the stationary device 20. The stationary device 20 determines the current position of the portable device 10 by using reception intensity data of the portable-device finding signals, which are received at the stationary-device side antennae, from the portable device 10.