A radio IC device includes a flexible dielectric base, a radiation element that is a metal film or a metal foil wrapped around the dielectric base, and a radio IC element mounted on the radiation element. The radiation element includes, in a portion other than a portion where the radio IC element is disposed, a bonded portion that is bonded to the dielectric element and a non-bonded portion that is not bonded to the dielectric element. The radio IC element is arranged to be directly opposed to the dielectric element with the portion of the radiation element where the radio IC element is disposed not bonded to the dielectric base.