the present invention relates to a radar device and , particularly , to a radar device mounted on a vehicle to be used for a collision alarm and the like . the invention provides a radar device that has a unit for removing the fmam noise without lowering the signal detection sensitivity . the radar device transmits a frequency modulation signal by switching the frequency modulation signal with a first switching signal , receives a signal reflected from a target object , switches the reception signal with a second switching signal , mixes the switched reception signal with the transmission signal , and further mixes the mixed signals with a third switching signal thereby to obtain a beat signal . the radar device obtains a distance to the target object and a relative speed of the target object from the beat signal . the second switching signal and the third switching signal have the same switching frequency , and have a predetermined phase difference between the phases of the two switching signals to cancel and remove an amplitude modulation component included in the frequency modulation signal .