An antenna device is constructed such that an antenna coil (202) including a magnetic core (4) and a flexible substrate (5) is mounted to a circuit board (9). A first coil portion (2a) having a coil axis parallel with a main surface of the magnetic core (4) includes a first coil (21) and a third coil (23). A second coil portion (2b) includes a second coil (22) and a fourth coil (24). A conductor-free portion (8) is located between the first and second coil portions (2a, 2b). The flexible substrate (5) includes a projection (6), and first to fourth coil connections are drawn out at the projection (6). The antenna device is constructed such that each of the coils is connected on the circuit board by connecting to a conductor pattern on the circuit board (9) at the projection (6) of the flexible substrate (5).