A radar device includes: an aperture surface including element antennas and phase shifters; an antenna phase control unit for calculating phase amounts based on a beam orientation direction and a rotation angle of the aperture surface; an antenna driving control unit for setting a rotation angle to a rotation mechanism; a signal processing unit for detecting a target with the use of the radar receiver, setting at least one of the rotation angle of the aperture surface or the beam orientation direction in the antenna driving control unit and the antenna phase control unit, and calculating the level of competing cluttering with the use of an antenna pattern, to thereby determine propriety of the rotation angle; and a pattern calculating unit for calculating the antenna pattern from the rotation angle of the aperture surface and from the beam orientation direction.