To realize a small and light-weight microstrip antenna which is difficult to receive influence from noise in a specific direction.

This strip antenna successively arranges a ground conductive board 2, a dielectric substrate 3 and a radiation conductive board 1 in the state of layers short-circuits one edge of the radiation conductive board 1 by a through hole string 4. Metallic bodies 5a and 5b being a radio reflector is arranged in parallel with and in the neighborhood of the orthogonal edge of the through hole strings 4 of the radiation conductive board 1 on the dielectric substrate 2. Reflecting surfaces 51a and 51b confronting the radiation conductive board 1 at the metallic bodies 5a and 5b reflects radio waves radiated from the radiation conductive board to generate indirect waves Wi1. At the time of making a direct wave from the radiation conductive board 1 and the indirect wave Wi1 the same phase remotedly, an antenna gain in the direction is increased and at the time of a reverse phase, the antenna gain in the direction is reduced to adjust antenna directional.