An ON/OFF detecting buckle switch includes: a case in a housing shape; a slider insertion port equipped in an upper face of the case; a support portion equipped in an inner side face of the case; a fixed terminal provided with a notched portion in one end in a strip shape and the other end fixed to the inner side face of the case; a movable terminal in a strip shape having one area fixed to the support portion; a slider provided with a terminal press portion that projects inside the case penetrating through the slider insertion port of the case and the notched portion of the fixed terminal, and when pressed down, presses down an end of the movable terminal; a spring that biases the slider upward; and bent portions in a hook shape in the notched portion of the fixed terminal and an end of the movable terminal.