A FM-CW radar device is provided for frequency-modulating a high frequency signal with a modulation signal, transmitting the modulated high frequency signal, receiving a signal reflected by a target object and frequency-modulating the reflection signal with a signal generated by a local oscillator signal source provided by branching a portion of the transmitting signal. A modulator is disposed between a radar transmitting section and a transmitting antenna. The modulator modulates the transmitting signal with a second frequency which is far lower than the radar transmitting frequency and twice as much as the sum or the difference of a Doppler frequency generated by a relative propagation velocity and a beat frequency generated by a propagation delay time. A first frequency converter frequency modulates the received signal reflected by the target object with the local oscillator. A second frequency converter frequency modulates the received signal with the second frequency, the second frequency being far lower than the radar transmitting frequency and twice as much as the sum or the difference of a Doppler frequency generated by a relative propagation velocity and a beat frequency generated by a propagation delay time.