PURPOSE: To form plural radiation beams with a reflection mirror antenna having one face by forming specular surfaces of both first and second reflection mirrors so that radiation waves from plural radio wave radiation sources placed near the first reflection mirror form individual focuses of less aberration near the second reflection mirror after being reflection on first and second reflection mirrors.

CONSTITUTION: A main reflection mirror 41 having the paraboloid of revolution, two reflection mirrors 42 and 43, and primary radiators 44 and 45 are provided. Radiators 44 and 45 are so arranged that their phase centers coincide with the entrance-side focus of a focusing beam transmission equipment. Therefore, radiation waves from radiators 44 and 45 are projected to the main reflection mirror 41 after forming focuses approximating each other of lees aberration at exit-side focuses 46 and 47. Thus, two beams 48 and 49 between which the interval is short are formed by an antenna having one face. Consequently, the degradation in characteristic for radiation of two beams from the antenna having one face is suppressed if this equipment is used in the focusing beam transmission system of the antenna, and the interval of radiation angle between two beams is very shortened.