An antenna device that includes a coil antenna with a coil conductor wound around a winding axis. The device further includes a planar conductor with a surface and an edge end portion, where the surface extends in the direction of the winding axis and the edge end portion is adjacent to a coil opening of the coil conductor. A booster antenna is also provided and includes a looped or spiral coil conductor and is coupled to the planar conductor and/or the coil antenna.