To identify multiple target objects having nearly equal distance and relative speed by detecting the peak frequencies of individual target objects, and detecting the existence information of individual target objects from the peak frequencies and the phase difference corresponding to them.

A triangular-wave modulation signal is generated by an FM modulator 10, an oscillator 12 is oscillated at the oscillation frequency corresponding to the modulation signal, and the transmission signal is transmitted from a transmission antenna 14. The reflected wave from a target object is received by reception antennas 20L, 20R, and reception signals are sent to mixers 24L, 24R. A part of the oscillation signal is mixed with the reception signals to generate beat signals by the mixers 24L, 24R, and the beat signals are sent to a fast Fourier transformer(FFT) 30. The power spectra and phase spectra of two beat signals in the frequency increase zone and frequency decrease zone of the transmission signal are obtained by the FFT 30 and are sent to a signal processing circuit 32. The existence information of individual target objects is detected from the peak frequencies and corresponding phase difference of the individual target objects by the signal processing circuit 32, and multiple target objects can be identified.