Antenna device

An antenna device incorporated in an electronic apparatus and communicating with an external device via an electromagnetic field signal, comprising:

• an antenna coil inductively coupled to the external device and provided by winding around a conducting wire such that conducting wires opposing in width direction via an opening will be close to each other;
• and a sheet-like conductor provided at a surface of the antenna coil opposite to a surface of the antenna coil opposing to the external device,
• wherein the antenna coil is divided into two parts, i.e. one side part in which the conducting wire is wound around in one direction and other side part in which the conducting wire is wound around in other direction, via a center line longitudinally traversing the opening, and
• the sheet-like conductor is configured to be provided with a conductor side opening overlapped only with the other side part of the antenna coil, and a slit formed between the conductor side opening and any outer edge of the sheet-like conductor.