PURPOSE: To use an antenna at a low frequency and to decrease the size of an antenna, by forming straight or curved slits in symmetry to two center axes thereon where rectangular or elliptic microstrip patch antennas are made orthogonal.

CONSTITUTION: The rectangular or elliptic patch conductor 2 is formed on the surface of a dielectric base 1 on the bottom of which a conductor 13 is placed and feeding points 5, 6 are provided on the center axes 3, 4 passing through the center of the rectangle or ellipse and orthogonal with each other respectively. Further, the straight or curved slits 7, 8 are provided in symmetry to the axes 3, 4 respectively. Plural number of the slits 7, 8 are arranged among the feeding points 5, 6 and the axial lines 3, 4 so as to decrease the resonance frequency of the antenna with the slits 7, 8, allowing to miniaturize the size of the microstrip antenna.