To obtain an antenna in which the thickness of a slot plate can be made thin, and the dimension of a slot can be realized with high precision, and inexpensive constitution can be realized even in the case of the high volume production of a large scaled array by butting the metallic face of a dielectric member to the rectangular recessed groove opening face of a waveguide array member having a T type waveguide part.

The metallic face of a dielectric member is butted to the rectangular recessed groove opening face of a waveguide array member having a T type waveguide part. In this antenna, a second dielectric plate 6 is arranged so that the face from which the dielectric of a part covering the rectangular opening face of a metallic block 7 constituting the T type waveguide is removed can be butted to the rectangular opening face corresponding to a rectangular recessed part 72 of the metallic block 7. Then, one opening face of a metallic block 5 constituting a waveguide array is butted to the metallic face of the second dielectric plate 6, and a first dielectric plate 1 is arranged so that a metallic foil 11 of the first dielectric plate 1 can be butted to the other opening face of the metallic block 5 constituting the waveguide array.