PURPOSE: To cut a flat glass plate in high squareness, preventing the generation of chipping, by placing a flat glass plate on a base table, lowering a cylinder head having a specific elastic member to contact the elastic member with the glass plate and applying hydraulic pressure force to the elastic member with a hydraulic unit.

CONSTITUTION: A hard rubber elastic member 11 to uniformize the cutting pressure over a definite width is attached to a cylinder head 12 having an oil channel to transmit oil-pressure 18 from a hydraulic unit to the elastic member 11 and the cylinder head 12 is made to be vertically movable with a cylinder 13. A flat glass plate 16 is placed on a base table 14 interposing a cushioning sheet 15 therebetween, the scribe line of the plate is positioned to the center of the elastic member 11 and the glass plate is fixed to the base table by vacuum suction. The cylinder 13 is lowered to contact with the flat glass plate 16 and oil-pressure 18 is applied to exert a compression force 19 to the elastic member 11 and generate concentrated stress to the part of the elastic member 11 contacting with the surface of the flat glass plate 16. The flat glass plate 16 is cut along the scribed line by the tensile force 20 caused by lateral elongation of the elastic member.