Provided is a contactless power supply antenna device that has raised power transmission efficiency while also enabling size-reduction for mounting on a wearable terminal or the like. The antenna device includes a power transmission antenna (2) and a power reception antenna (3). The power transmission antenna (2) includes: a magnetic core including two magnetic plates (21) that face each other, a magnetic material-containing connecting portion (22) that connects at least part of an end section of each of the two magnetic plates (21), and a space (23) between the two magnetic plates (21); and a power transmission coil (25) disposed on at least one of the two magnetic plates (21) at a side thereof that faces the space (23). The power reception antenna (3) includes a power reception coil (31) and is positionable in the space (23).