A transmission antenna unit includes transmission antennas arranged in a row along a predetermined array direction at a predetermined first interval. A reception antenna unit includes reception antennas arranged in a row along the array direction at a second interval set to differ from the first interval. The transmission antennas and the reception antennas form a virtual array in which virtual reception antennas are arranged in a row along the array direction. The first interval is equal to a multiplication value of a minimum interval being a minimum value of an arrangement interval of the virtual reception antennas and a first multiple being an integer of 2 or greater. The second interval is equal to a multiplication value of the minimum interval and a second multiple being an integer of 2 or greater and set to differ from the first multiple. The first and second multiples are coprime.