A wireless IC device prevents deviations of the resonant frequency from the desired value. An antenna coil has an end portion positioned in a connector provided on the negative-most side in the z-axis direction and an end portion positioned in a connector provided on the positive-most side in the z-axis direction. A wireless IC is electrically connected to the end portions. A via hole conductor is provided between the end portion and the wireless IC and penetrates through a plurality of insulator layers. A via hole conductor is provided in the antenna coil such that the length of a current path thereto from the end portion is the shortest among a plurality of via hole conductors. The distance between the via hole conductor and the via hole conductor is larger than the distances between the penetrating via hole conductor and the via hole conductors.