A stop switch assembly includes a movable block, a pressing portion, a driving rod, a driving pin and an elastic member. The movable block includes a first pair and a second pair of opposite side surfaces, a hole is defined in the movable block passing through the first pair of side surfaces and an inclined slot is defined in the movable block passing through the second pair of side surfaces. The driving pin is inserted in the driving rod with its head movably arranged in the inclined slot. The elastic member is arranged between the pressing portion and the movable block for applying an elastic bias to the pressing portion to allow the pressing portion being away from the movable block. When the pressing part is pressed, the driving pin slides in the inclined slot and drives the movable block moving between a first position and a second position.