PURPOSE: To obtain the thickness of the optical master disk with good accuracy by providing a recess of the same thickness as the thickness required after the optical master disk is polished to a substrate to be stuck with the optical master disk and sticking the optical master disk to this recessed part, then polishing the master disk.

CONSTITUTION: Materials harder than the optical master disk 33, for example, glass, stainless steel, etc., are used for the material of the substrate 30 to be stuck with the optical master disk 33 and the recess is previously provided to the substrate by as much as the sized required for sticking the optical master disk 33 after the optical master disk 33 is polished. The optical master disk 33 with the surface to be polished faced upward is stuck to this recessed part and is subjected to polishing. The polishing is executed for the time until the thickness of the optical master disk 33 coincides with the height of the recess of the substrate 30. The optical master disk is finished to the thickness of the high accuracy in this way.