PURPOSE: To improve a wide angle directivity by providing N sets of reflecting plate elements to a support supporting a primary radiator or the like, devising properly the elements so as to spread a scattered wave reflected, diffracted from he support and irradiated concentratingly in a specific direction.

CONSTITUTION: Reflecting plate elements 2-1∼2-7 are arranged continuously to the side face of the support 1 at the side of the primary radiator or a sub reflection mirror at the side of a main reflection mirror. The reflecting plate elements 2-1∼2-7 are arranged to the side face of the support 1 at the main reflection mirror to a plane wave 102 coming along the progressing direction 101 from the main reflection mirror at an interval L, which is selected larger than the wavelength of the operating radio wave and the side of the elements is formed as a curved line. The elements are arranged so that the tilt angle of a planer reflecting face of each element has respectively increased as the value (i) increases. Thus, the plane wave 102 coming from the main reflection mirror is scattered by each reflecting plane of the elements.