To prevent any unnecessary card data from being read from the back face side of an antenna, and to make this device compact and lightweight by shielding the radiation of an electromagnetic wave to the back face side of an antenna in a simple structure.

A box 3 formed of conductive materials such as iron is arranged in a wall 2. A mounted member 4 on which an identifying device 1 is mounted is integrated into the box 3, and an outer wall 2A is interposed between this mounted member 4 and the box 3. A back face part 3A of the box 3 shields an electromagnetic wave radiated from an antenna 9 to the back face side. When the mounted member 4 is mounted to the box 3, an interval between the antenna 9 and the back face part 3A is set as a prescribed interval. Thus, the preliminarily decided frequencies of the electromagnetic wave radiated from the antenna 9 can be made coincident with the resonance frequencies of an LC resonance circuit.