Disclosed herein is an antenna device that includes a substrate, a conductor pattern formed on the substrate, and a magnetic sheet formed on the substrate. The conductor pattern includes a spiral or loop-shaped antenna coil and a spiral or loop-shaped coupling coil connected to the antenna coil and having a diameter smaller than that of the antenna coil. The antenna coil overlaps the magnetic sheet. The magnetic sheet has a first opening at a position overlapping the coupling coil such that an inner diameter area of the coupling coil completely overlaps the first opening in a plan view.