To provide an IC card device and an adaptor used for the IC card device constituted by mounting a thin IC card to the adaptor and provided with the adaptor securing the maximum thickness formed by the lower face of the adaptor and a face mounted with the IC card so as to function as the IC card of specified specification.

The IC card 1 is provided with protrusions 11, 12 along the left and right side faces, and an electrical connecting terminal 5 disposed at the lower face. The plate-like adaptor 2 is provided with a storage recessed part 3 for enclosing the IC card 1, opened at an upper face 4 and one end 7. The storage recessed part 3 is provided with grooves 21, 22 fitted to the protrusions 11, 12 along the left and right side faces, and an electrical connector 6 connected to the electrical connecting terminal 5, at the bottom face. The IC card 1 is inserted in the storage recessed part 3 from one end 7, and the electrical connecting terminal 5 is connected to the electrical connector 6 to constitute the IC card device.