An RFIC tag includes an IC chip and a thin metal plate. The IC chip is mounted approximately in the center of a slit part on the thin metal plate. The thin metal plate has connecting parts at both longitudinal-direction ends fixed on a metal member by soldering, and the undersurface of the slit part, which has an L-shaped slit thereon, is lifted a predetermined height from the surface of the metal member. The total length (L2+L1+L2) is 1/4 or shorter than the communication wavelength .lamda..