Disclosed herein is an antenna device that includes a substrate; a conductor pattern formed on the substrate and including a spiral or loop-shaped antenna coil, a spiral or loop-shaped coupling coil being connected to the antenna coil and having a diameter smaller than that of the antenna coil, and a spiral-shaped booster coil at least partially overlapping the antenna coil through the substrate without being connected thereto; and a resonance capacitor connected to the booster coil. The number of turns of the booster coil is larger than that of the antenna coil.