The invention provides a building hardware steel plate cutting device and belongs to the field of building cutting. The building hardware steel plate cutting device comprises a cutting box, a glass plate, a movable sliding block, a steel plate pressing carrier plate, a rubber pressing plate, a cutting device body and sliding grooves. The cutting box is arranged on the horizontal working face. Twosliding grooves are formed in the protruding wall of the right end of the lower end in the cutting box. The glass plate is fixedly arranged in the right side wall of the cutting box in an inlaid manner. The lower side of the left end of the movable sliding block is arranged in the two sliding grooves. The left end of the movable sliding block is arranged on the right side of the glass plate through the moving groove. The movable sliding block can move in the two sliding grooves. The cutting device body is welded to the left side face of a connecting rod. The steel plate pressing carrier plateis welded to the left side face in the cutting box. The rubber pressing plate is fixedly arranged in the lower end of a lead screw through a first bearing. The device is reasonable in design, firm tofix, high in cutting precision, high in practicality and good in development prospect.