To accurately detect a relative speed to an object by finding, as the pulse interval of a reflected wave, the pulse interval of a waveform whose calculated correlation value is the largest out of a first predetermined number of waveforms stored in a first waveform storage means, and acquiring the accurate pulse interval of the reflected wave.

An object detecting ECU 1 includes; a radar signal transmitting part 21 for transmitting a transmission wave composed of a group of pulses which comprise pulses corresponding to two or more pulses and have a preset pulse interval; the first waveform storage part 111 which stores information on the first predetermined number, two or more, of waveforms having mutually different pulse intervals beforehand, as candidates for the waveform of the reflected wave received by a radar signal receiving part 22; a first correlation value calculation part 112 for finding a correlation value between each of the first predetermined number of waveforms stored in the first storage part 111 and a reflected wave signal acquired by a received signal acquisition part 102; a first interval determination part 113 for finding as the pulse interval of the reflected wave, the pulse interval of the waveform whose calculated correlation value is the largest out of the first predetermined number of waveforms stored in the first storage part 111; and a relative speed calculation part 115 for finding the relative speed to the object based on the acquired pulse interval.