An antenna includes a flexible sheet that includes a first main surface including a first coil electrode located thereon and a second main surface including a second coil electrode located thereon. The first and second coil electrodes are wound in opposite directions when viewed from different directions. A first end of the first coil electrode faces a first end of the second coil electrode through the flexible sheet. Similarly, a second end of the first coil electrode faces a second end of the second coil electrode through the flexible sheet. The first and second coil electrodes define an inductor, the first ends of the first and second coil electrodes define a capacitor, and the second ends of the first and second coil electrodes define a capacitor whereby a resonant antenna is provided.