Provided is a radio IC device which is hardly affected by a use environment and can be used in a wide range while suppressing fluctuations of radiation characteristic. The radio IC device includes: a radio IC; a power feed circuit substrate (20); and a radiation plate (52). The power feed circuit substrate (20) is electrically connected to the radio IC and has a built-in power feed circuit (21) having a resonance circuit including inductance elements (L1, L2, L3, L4) and/or a rectification circuit. The power feed circuit substrate (20) is bonded to the radiation plate (52). The radiation plate (52) emits a transmission signal supplied from the power feed circuit (21) and supplies a received signal to the power feed circuit (21). The inductance elements (L1, L2) and the inductance elements (L3, L4) are spirally wound respectively in opposite directions and connected to each other with inverse phases.
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