A radar device that detects a target includes two or more transmitting antennas and two or more receiving antennas, including a combination of two or more transmitting antennas and receiving antennas that form two or more reference paths at which spatial phases become identical; an envelope detection unit that acquires an envelope of a reception signal received by the receiving antenna in each of the reference paths; a determination unit that decides a phase correction amount between the reference paths from a delay amount that yields a minimum value of an integrated distance between envelopes of the reception signals of the reference paths; and a correction unit that aligns phases of all reception signals received by the two or more receiving antennas, using the decided phase correction amount.