The invention relates to equipment for machining metallic sheet metal pieces, in particular to a flat edge-trimming machine. The flat edge-trimming machine mainly comprises a frame (1), an electrical appliance control box (2) and a braking motor (3) which are arranged in the frame (1), an oil cylinder or cylinder device which is arranged on the upper part of the frame (1), a die assembly (39) which is divided into upper and lower parts, a transmission component which transmits the power of the braking motor (3) to the lower part of the die assembly (39), and a guide oil cylinder or cylinder (35) which ensures that the lower part of the die assembly resets, wherein the transmission component comprises a spindle (8); and the spindle (8) in the transmission component is directly connected with a braking motor shaft (4) on the braking motor (3) through a chain wheel, and the power of the braking motor (3) is transmitted to the spindle (8) after a braking motor shaft single-row chain wheel (5) on the braking motor shaft (4) is engaged with a spindle single-row chain wheel (7) on the spindle (8). The invention is characterized in that the flat edge-trimming machine can trim regularly, is low in cost, and is safe and reliable; and the flat edge-trimming machine can easily remove excess materials on the edges of drawn pieces, so that the processes are simplified, the labor intensity of workers and the machining time are reduced, the production efficiency is improved, and accident work injuries can be avoided.