Microstrip antenna

A plurality of antenna electrodes on a substrate can be connected to a ground electrode on the substrate via connectors at spots A-C, A-C, A-C, and A-C. Each connector can be opened/closed by a switch; or provided with a impedance varying device. Any one of the antenna electrodes may be connected to the ground electrode by the switch or the impedance varying device. The radio wave beam outputted from this antenna electrode shifts in phase from the radio wave beams outputted from the other antenna electrodes, whereby the direction of the integrated radio wave beam is inclined. Connecting one or another of the spots A-C, A-C, A-C, and A-C to the ground electrode changes the direction and the magnitude of the integrated radio wave beam.