A plate making apparatus of a flexible plate material 13,22 being placed on a plate cylinder 7 for executing planographic printing in multiple colors. The plate making apparatus has a cutter 23 being placed between a storage section 21 of a roll-like plate material and an exposure section 25 for cutting the roll-like plate material like a sheet and punch means 30 for making plate cylinder engagement holes 14a and 14b in the left and right margins of the plate material along the transport direction thereof, the plate cylinder engagement holes to be engaged in protrusions 7a and 7b disposed in the circumferential direction of the left and right margins of the plate cylinder. Accordingly, it is possible to provide a plate making apparatus which reliably holds a plate material on a plate cylinder for enabling planographic printing and can use a roll-like plate material.