To allow waveguide wide-pipe-wall slot array antennas, which are arranged having narrow-pipe-wall surfaces in contact, to generate a horizontally polarized wave, a vertically polarized wave, a circularly polarized wave, and an obliquely polarized wave by setting the array of the waveguides to 1/2 of smaller as large as the wavelength and devising the positions of slots provided at wide pipe walls.

This antenna has waveguides 11 to 13, which each have plural slots A. The waveguides 11 to 13 are filled with dielectrics, and the distance of the slots A on the tube axis is set to λg'/2 and the horizontal distance is set to λ'/2. Element intervals are set equivalently to a half as long as the wavelength by the dielectrics. Here, the arrows crossing the slots A show current flowing on the wall surfaces.