A microwave transponder. The microwave transponder includes a conductive plate including an antenna, and a semiconductor chip disposed within a terminal gap located in a vicinity of a center of the conductive plate. A window of a predetermined shape is formed to extend from the terminal gap toward a side of the conductive plate. The perfect impedance matching is fulfilled even when the transponder is bent. Since the return loss of the electromagnetic power is reduced at least in a quarter through the impedance matching, the energy transferred to the transponder is maximized.