An electronic apparatus comprising a casing and incorporating an antenna device configured to communicate with an external device via an electromagnetic field signal, wherein the antenna device comprises: a first electric conductor facing with a first surface a first surface of the casing to which the external device is to be applied; an antenna coil configured to be inductively coupled to the external device; a second electric conductor in sheet form, the second electric conductor overlapping or being in contact with the first electric conductor, and at least partially overlapping a surface of the antenna coil, the surface being opposite to the first surface of the first electric conductor; and a communication processing unit configured to communicate with the external device, wherein the second electric conductor overlaps one side of the antenna coil, the one side having a lead wire wound around thereon in one direction, and does not overlap another side of the antenna coil, the another side having the lead wire wound around thereon in another direction, characterised in that said antenna device further comprises a magnetic sheet configured to induce a magnetic field transmitted from the external device in the antenna coil, wherein the antenna coil and the magnetic sheet overlap each other in such a way that said magnetic sheet is inserted into a center portion of said antenna coil, thereby satisfying both disposition conditions, one of the disposition conditions being such that, on a center side of said first surface of said casing, said magnetic sheet is positioned closer to the first surface of said casing than said antenna coil is, another one of the disposition conditions being such that, on an outer circumference side of said first surface of said casing, said antenna coil is positioned closer to said first surface of said casing than said magnetic sheet is. a first electric conductor facing with a first surface a first surface of the casing to which the external device is to be applied; an antenna coil configured to be inductively coupled to the external device; a second electric conductor in sheet form, the second electric conductor overlapping or being in contact with the first electric conductor, and at least partially overlapping a surface of the antenna coil, the surface being opposite to the first surface of the first electric conductor; and a communication processing unit configured to communicate with the external device, wherein the second electric conductor overlaps one side of the antenna coil, the one side having a lead wire wound around thereon in one direction, and does not overlap another side of the antenna coil, the another side having the lead wire wound around thereon in another direction, characterised in that said antenna device further comprises a magnetic sheet configured to induce a magnetic field transmitted from the external device in the antenna coil, wherein the antenna coil and the magnetic sheet overlap each other in such a way that said magnetic sheet is inserted into a center portion of said antenna coil, thereby satisfying both disposition conditions, one of the disposition conditions being such that, on a center side of said first surface of said casing, said magnetic sheet is positioned closer to the first surface of said casing than said antenna coil is, another one of the disposition conditions being such that, on an outer circumference side of said first surface of said casing, said antenna coil is positioned closer to said first surface of said casing than said magnetic sheet is.