Gaussian-beam antenna

A Gaussian-beam antenna invention comprises a transmitting circuit or a receiving circuit, a resonator consisting of a pair of reflecting mirrors, which consist of a spherical mirror and a planar mirror or two spherical mirrors, and a transmission line which transmits a high-frequency signal between the aforesaid transmitting circuit or receiving circuit and the resonator, one reflecting mirror of the resonator having an electromagnetic wave coupling region constituted as a circular partially transparent mirror surface region having its center on the optical axis.