PURPOSE: To improve both the cross polarized wave characteristic and the beam shaping by combining beams in a vertical plane by means of an array antenna and combining beams in a horizontal plane by means of a cylindrical mirror surface.

CONSTITUTION: The array antenna 40 as a radiator consists of a waveguide slot antenna and the main reflecting mirror consists of a cylindrical mirror surface comprising partial cylindrical mirror surfaces 50, 51, 52. The main reflecting mirror is provided with a converting section 42 as fitting structure to mount the antenna 40. The lengthwise direction of the antenna 40 is taken as the X axis. The cylindrical axis of the partial cylindrical mirror surfaces 50, 51 is arranged in parallel with the X axis and the entire cylindrical mirror surface is symmetrical with respect to the XZ plane. A focal line 53 is a line near the X axis and in parallel therewith. The slot of the antenna 40 is excited by a current of the waveguide, the amplitude is adjusted mainly by the dimensions S and the relative exciting phase among slots is adjusted mainly by the dimension L. Then no cross polarized wave component is included basically in the wave source by using an element having excellent cross polarized wave identification as each radiation element and the beam shaping is attained. Thus, the excellent cross polarized wave characteristic is obtained without cancelling the cross polarized wave component included in the wave source.