PURPOSE: To accurately detect a short range object irrespective of a radar modulation system by interposing a delay circuit between a transmission/ receiving output/input part and a transmission/receiving circuit part.

CONSTITUTION: A delay circuit 12 is interposed between a transmission/receiving output/input part 11 and a transmission/receiving circuit 13, or a delay circuit 15 is interposed between a transmission output part 14 and a transmission/ receiving circuit 16 with a delay circuit 17 being interposed between a receiving input part 18 and the transmission/receiving circuit 16. In the case of an electric wave radar, the transmission/receiving output/input part 11, the transmission output part 14 and the receiving input part 18 are constituted of antennas while the delay circuits 12, 15, 17 are constituted of waveguides or dielectric lines or the like. In the case of a laser radar, the transmission/receiving output/input part 11, the transmission output part 14 and the receiving input part 18 are constituted of lenses while the delay circuits 12, 15, 17 are constituted of optical fiber and the like. The radar can accurately detect an object of a short range including zero meter irrespective of a modulation system thereof.