PURPOSE: To easily and simply make a both-side master in a short time by providing a controller which changes the formed position of an original image for a master for printing in accordance with a moving amount by the selection of a manual operation key.

CONSTITUTION: A value expressing the moving amount from the leading edge of an original as (DG-f.(m+1/m-2.0534).m)/LS and (L-DG-f. (m+1/m-2.0534).m)/ LS (DG: a gripper space from the leading edge of a front surface side master, f: the focal distance of an optical system, m: magnification, LS: the unit moving amount of the master, and L is the length of the master) is stored in the memory 42 of a plate making machine. The manual operation keys K1 and K1 capable of selecting whether the original is the front surface side master or the back surface side master are installed and the controller 40 which changes the formed position of the original image for the master in accordance with the moving amount by the selection of the keys K1 and K2 is provided.