An antenna that suppresses deterioration of communication performance depending on an angle with respect to a reading surface of a reader/writer includes a rectangular spiral coil conductor provided on a flexible substrate. The flexible substrate includes an aperture in a winding center portion of the coil conductor. A magnetic sheet penetrates the aperture of the flexible substrate. An antenna coil is provided near an end of a circuit board. A first conductor portion and a second conductor portion of the coil conductor are provided at positions opposing each other across the aperture. A portion of the magnetic sheet close to the second conductor portion is bent in a direction to get close to the circuit board.