Antenna device and communication terminal device

An antenna device comprising:

• a power feed coil antenna connected to a power feed circuit;
• and
• a booster coil antenna including a wound coil conductor and disposed so as to be electromagnetically coupled to the power feed coil antenna;
• wherein
• the power feed coil antenna includes a first coil antenna and a second coil antenna each including a coil conductor, the coil conductor of the first coil antenna and the coil conductor of the second coil antenna being connected in phase with each other;
• the first coil antenna is disposed such that a winding axis of the coil conductor of the first coil antenna extends perpendicularly or substantially perpendicularly to a winding axis of the booster coil antenna, and such that at least a portion of the first coil antenna overlaps the coil conductor of the booster coil antenna as viewed in plan;
• and
• the second coil antenna is disposed in a vicinity of the coil conductor of the booster coil antenna such that a winding axis of the coil conductor of the second coil antenna extends parallel or substantially parallel to the winding axis of the booster coil antenna, and such that at least a portion of a coil opening of the second coil antenna does not overlap the coil conductor of the booster coil antenna as viewed in plan.