PROBLEM TO BE SOLVED: To provide an RF tag with high communication performance, which can be mounted in a void included inside a member made of a conductor.SOLUTION: An RF tag 1 according to an embodiment of the present invention is an RF tag mounted in a void 101 included inside a member 100 made of a conductor. The RF tag at least includes: a free space antenna 10； a resonant circuit 20； an IC chip 30； a closed space antenna 40； and a substrate 50 for supporting the closed space antenna. A part of the free space antenna is exposed to the outside from the void, and the substrate supports the closed space antenna so that the closed space antenna is not in contact with an inner surface of the member made of a conductor. A capacitor portion C2 is formed by the closed space antenna, the substrate, and the member made of a conductor. This structure electrically couples the closed space antenna to the member made of a conductor, electrically coupling the IC chip that is connected with the closed space antenna, to the member made of a conductor. Thus, the whole of the member made of a conductor can be used as an antenna.SELECTED DRAWING: Figure 1【課題】 内部に空隙を有する導体製の部材に対して、当該空隙内に取り付けることができ、且つ高い通信性能を有するRFタグを提供する。【解決手段】 本発明のRFタグ1は、内部に空隙101を有する導体製部材100の当該空隙内に取り付けられるRFタグであり、自由空間アンテナ10と、共振回路20と、ICチップ30と、閉鎖空間アンテナ40と、当該閉鎖空間アンテナを支持する基板50を少なくとも備えており、自由空間アンテナはその一部が空隙から外部に露出しており、基板は前記閉鎖空間アンテナを前記導体製部材の内面に接触させずに支持する。閉鎖空間アンテナ、基板及び導体製部材でコンデンサ部C2が形成される。これにより、閉鎖空間アンテナと導体製部材とが電気的に接続されることになり、閉鎖空間アンテナに接続するICチップと導体製部材とを電気的に接続して、導体製部材全体をアンテナとして利用できる。【選択図】図１
