An antenna device incorporated in an electronic apparatus and communicating with an external device via an electromagnetic field signal, including: an antenna coil inductively coupled to the external device and provided by winding around a conducting wire in planar shape; a magnetic sheet arranged to overlap with the antenna coil mutually along the antenna coil by inserting the magnetic sheet into a coil opening provided at center side of the antenna coil; and a metallic cover formed with an opening near an end of the metallic cover and arranged at surface side of the antenna coil opposing to the external device, wherein the antenna coil is arranged to overlap with the metallic cover in a region between the opening and the end of the metallic cover at a backside surface of the metallic cover opposite to a surface of the metallic cover opposing to the external device.