PURPOSE: To facilitate an excellent circularly polarized wave by providing the 1st feeding point on the center line of an antenna and arranging two of the 2nd feeding points on the same line or symmetrically mutually so as to decrease the adverse effect on the electric characteristic such as the axial ratio due to the undesired harmonic mode.

CONSTITUTION: The microstrip antenna 100 is subjected to processing such as increase in the thickness of a dielectric base 2 or decrease in the dielectric constant so as to be made suited to proper broad band. Further, the 2nd feeding points A7, B8 as the 2nd feeders are provided to the microstrip antenna 100 symmetrically to the center line passing through the center point O of the radiation element 1 at an equal distance and the 2nd feeding point 9 as the 2nd feeder is provided on the center line of the antenna on the same line of the 1st feeder. A power distributor 200 excites the microstrip antenna 100 by feeding the power with the prescribed condition to the feeding points 7, 8 and 9.