The present invention provides an antenna in which a single exciting point can be commonly used by a plurality of frequencies, particularly, a small multi-mode plate antenna, and a small and cheap multi-media wireless apparatus using the antenna. In the antenna, a slit 2 is formed in a conductive plate 1, and resonance is made at an exciting point 3 provided in a part of the conductive plate around the slit 2. Further, enclosed openings 4, 6 are formed in parts which are capacitive when seen from the exciting point 3 on the conductive plate 1, and inductances are formed by conductive strips 5, 7 in the enclosed openings 4, 6 respectively. Another resonance is generated by the conductive strips 5, 7. In such a manner, resonances corresponding to a plurality of frequencies are realized at the exciting point 3.