The present invention is concerned with a transmitting/receiving antenna, which includes a dielectric board, a driven loop antenna provided to the dielectric board, transmit processing portion connection terminals connected to the driven loop antenna, a transmitting/receiving loop antenna arranged in close vicinity to the driven loop antenna in a non-contact state, a resonance capacitor connected to both ends of the transmitting/receiving loop antenna, and receive processing portion connection terminals connected to the transmitting/receiving loop antenna. The driven loop antenna is constructed to have a loop wound in a single turn, and the transmitting/receiving loop antenna is constructed to have a loop wound in plural turns. According to this configuration, a wider frequency band of the frequency characteristic and a reduction of the power consumption can be achieved.