PURPOSE: To make the frequency characteristic of impedance wide and to reduce the mutual coupling between element antennas by providing 2nd and 3rd ground conductors at both sides of a square patch in parallel with a face orthogonal to a radiation electric field face.

CONSTITUTION: A patch 1 of a metallic foil is formed on one face of a dielectric body 2 and a ground conductor 3 made of a metallic foil is provided on the other side in a microstrip antenna, and 2nd and 3rd ground conductors 7, 8 are provided to both sides of the patch 1 in parallel with a face orthogonal to a radiation electric field face of the square patch 1. The 2nd and 3rd ground conductors 7, 8 act equivalently like a monopole antenna, the field is interacted with a radiation electromagnetic field of the square patch 1 to show a broad hand characteristic. Moreover, the 2nd and 3rd ground conductors 7, 8 are barriers between element antennas in the array antenna where lots of element antennas are arranged to reduce the interacting coupling quantity.