A control gate includes an exciting coil and a detecting coil. The exciting coil forms an alternating magnetic field in a passageway at an entrance to or an exit from an area where taking out or bringing in of an object is controlled. The detecting coil detects a change of the magnetic field when magnetic substance contained in the object generating a large Barkhausen effect causes magnetic inversion in the alternating magnetic field. The exciting coil is provided above the passageway and has a winding wire wound along a horizontal plane. The detecting coil is provided in a side part of the passageway and has a winding wire wound along a vertical plane which is parallel to a passing direction of the passageway.