A pushbutton switch has a pushbutton having a slot receive therein a free end of the linkage and a receiving space in communication with the slot so as to allow the free end of the linkage to move toward the receiving space when an electrical overload occurs in the pushbutton switch. The linkage has a cutout defined in the second distal end to have a portion of the heat sensitive plate to be received in the cutout and an extension formed with the linkage and extending out into the slot. Therefore, when the heat sensitive plate reacts to heat and curves to cause the first contact to separate from the second contact, a free end of the linkage received inside the slot is able to move toward the receiving space to allow a free movement of the heat sensitive plate without any limitation to hinder the curvature movement of the heat sensitive plate.