A wireless IC device includes a spiral line electrode portion and a first capacitance electrode connected to the inner end of the line electrode portion, which are disposed on the top surface of a substrate. A second capacitance electrode opposing the first capacitance electrode and a cross line electrode, which connects the second capacitance electrode and a connecting portion that connects the top and bottom surfaces, are disposed on the bottom surface of the substrate. The connecting portion electrically connects the outer end of the line electrode portion and an end of the cross line electrode. A wireless IC is mounted such that terminal electrodes thereof are connected to the connecting portion and an end of a radiating electrode. A radiating/resonating electrode including the line electrode portion, the capacitance electrodes, and the cross line electrode can act both as a resonant circuit for a resonant tag and as a radiating electrode serving as an RFID tag.