PURPOSE: To prevent the edge from adhering ink during printing operation by a device wherein a cut is provided for the square edge section of aluminum supporter of offset plate.

CONSTITUTION: Before or after graining, or before or after coating a sensitive liquid, the edge cross section of two sides or four sides of aluminum supporter for the plate are deformed. The shape of the deformed cut 5 is acceptable with the shape no ink adhered during printing operation, for example, with X:Y=1:0.17W 1:1, x>5μ holding, then a stain will be minimized remarkably. Further, the straight or curved line joined with a and b lines may eliminate the burrs, and also weaken the touch against a blanket. Whenever the edge is shaved or broken up, the stains may be eliminated remarkally by setting the angle θ between 10W45 degrees.