A detect switch (100) includes an insulative housing (2), a first, a second, a third and a fourth fixed terminals (11, 12, 13, 14), a moveable contact (3) electrically connecting with the third and the fourth fixed terminals, a driving mechanism depressing the moveable contact. The moveable contact has four periphery contact portions (32) each formed with a protrusion (33). One of the protrusions resists against the third fixed terminal in assembly. When the moveable contact is depressed to have a central contact portion (31) thereof contact with the first fixed terminal, the periphery contact portions tilt upwardly to leave away from corresponding fixed terminals for insulating the third and the fourth fixed terminals. The third and first fixed terminals are thereby electrically connected due to an engagement among the moveable contact and themselves.