In an antenna apparatus, on an undersurface of a metal cover, a feeding coil module is disposed. In a casing, a printed circuit board is included. A ground conductor, a feeding pin, and a ground connection conductor are disposed on the printed circuit board. When the metal cover is mounted on the casing, the feeding pin is in contact with a connection portion of the feeding coil module and is electrically connected thereto. The ground connection conductor is in contact with the metal cover and connects the metal cover to the ground conductor. The ground connection conductor is disposed at either side of a slit outside an area in which the current density of an induced current flowing through the metal cover is in a range from a maximum value to approximately 80% of the maximum value or one side of the slit in the area.