A step flashing bending device comprises a supporting a lower press block and an upper press block thereon for movement relative to one another for bending blank metal sheets into step flashing therebetween. The press blocks have working surfaces which are elongate in a longitudinal direction extending at a downward inclination from a top end to a bottom end thereof. The frame and the press blocks are open at the bottom end such that the working surfaces are arranged to automatically release the step flashing from the frame between the bottom ends of the upper and lower press blocks under force of gravity when the press blocks are separated into an open position.