One of a transmitting array antenna and a receiving array antenna includes a first antenna group and a second antenna group. The first antenna group includes one or more first antenna elements of which the phase centers of the antenna elements are laid out at each first layout spacing following a first axis direction, and a shared antenna element. The second antenna group includes a plurality of second antenna elements and the one shared antenna element, and the phase centers of the antenna elements are laid out in two columns at each second layout spacing following a second axis direction that is different from the first axis direction. The phase centers of the antenna elements included in each of the two columns differ from each other regarding position in the second axis direction.