Abstract: To provide a compact and light broad range antenna apparatus transmitting and receiving an electric wave in GHz frequency band (wavelength: ?), a flat shaped antenna element (10), where a length b? in an X-axis direction is less than ?/4 and a length a? in a Y-axis direction is less than ?/4, is arranged at a distance j less than ?/4 from a ground plate (2) in the Y-axis direction and connected to a high-frequency power source (9), and an enlarged flat shaped parasitic element (15) is structured by connecting a base portion (13) having approximately the same shape and dimension as those of the antenna element (10) with an extension portion (14) extending from the base portion (13) in the X-axis direction so as to face to the antenna element (10) with a distance, and connected conductively with the ground plate (2) by a ground line (5).