A wireless IC device that improves radiation gain without increasing substrate size and easily adjusts impedance, includes a multilayer substrate including laminated base layers. On a side of an upper or first main surface of the multilayer substrate, a wireless IC element is arranged to process a high-frequency signal. On a side of a lower or second main surface of the multilayer substrate, a first radiator is provided and is coupled to the wireless IC element via a feeding circuit including first interlayer conductors. On the side of the first main surface, a second radiator is provided and is coupled to the first radiator via second interlayer conductors.