The present invention provides a wireless tag to be attached onto a disc-shaped recording medium including first and second regions. The first region, made of a nonconductive member, is disposed on the inner radial part of the recording medium, whereas the second region, including a conductive member, is disposed on the outer radial part of the recording medium. The wireless tag includes: a feed section connected to a wireless IC chip; a conductive plate including a slot therein; and a slot antenna for receiving power from the feed section. The conductive plate is formed for at least partially overlapping with the second region when the wireless tag is attached onto the inner radial part of the recording medium. The slot has a length set for obtaining an inductance enough to cause a resonance between the slot antenna and the wireless IC chip at a predetermined wireless frequency.