An incorrect-circuit deactivation device of a magnetic GFCI outlet includes an electromagnetic coil seat, a magneto-conductive core driven by the electromagnetic coil seat to displace, and two magnetic elements located on both sides of the magneto-conductive core. The magneto-conductive core is connected to a first electrical conductive end. The first electrical conductive end is positioned to face a second electrical conductive end. Electric power is supplied when the first electrical conductive end is brought into contact with the second electrical conductive end. The electromagnetic coil seat senses a reverse current to make the magneto-conductive core to displace toward one of the magnetic elements when there is a ground fault, thereby departing the first electrical conductive end from the second electrical conductive end to cut off the electric current.