To make the reflector of a satellite antenna in a communication satellite system select frequencies.

An inside reflector portion 12 of a reflector 10 reflects both up and down link signals such as signals of 20 GHz and 30 GHz and the outside reflector portion 14 reflects only the 20 GHz signal in the direction of a primary beam. As a result, an electric aperture to the reflection plane of30 GHz is of the diameter of the inside reflector portion 12, and an electric aperture to the reflection plane of 20 GHz is of the full diameter of the frequency selecting reflector 10. Since a beam width is in reverse proportion to the diameter, the inside reflector portion 12 becomes 2/3 the entire reflector 10. Concerning equalization of the beam width to the 20 GHz and 30 GHz signals, a feed 16 overlaps the beam pattern of 20 GHz on the beam pattern of 30 GHz and performs both transmission and receiving of signals between the satellite and the same prescribed block on the ground.