A photomask capable of preventing a pattern outside a chip region from being transferred onto a wafer. The first device connects to a switched outlet and sends a signal to the second device when the outlet is turned on or off. A plurality of dummy patterns 13 are located in the wiring layer in which the signal wiring patterns 3 are formed, so as to be inclined at an angle of generally 45 degrees toward the associated signal wiring patterns 3. The two pistons are connected to each other through a shift cylinder and are disconnected by the pressure relief in a second pressure chamber through the shift cylinder in such a way that the piston is displaceable by a spring-loaded spring.