A DBF antenna unit including one or more transmitting antennas and a plurality of receiving antennas arranged at a predetermined interval in a horizontal scanning direction. Each of the transmitting antennas and the receiving antennas includes a waveguide provided with a corner bend and a horn expanding in a pyramid-like shape from one end of the waveguide. The other ends of the waveguides of all the transmitting antennas and the receiving antennas are placed on the same plane.