PURPOSE: To enable the photo mask to make close contact well to the original spherical or curved face and obviate its deformation by forming a mask body by a metal mask of copper or the like and a film of plastics transparent to ultraviolet rays to be fitted to the outside circumference of said mask.

CONSTITUTION: A polished steel ball is dipped in a copper sulfate solution to form a plating layer 12 of about 15 to 20μ on the surface through copper electroforming and further photoresist 13 is coated on the outside circumference of the plating layer, after which an arbitrary pattern is transferred and etched, whereby a metal mask 14 which has no internal stress and will not deform is formed. Next, a film 15 of about 0.5 mm which is composed of vinyl chloride or the like and is transparent to ultraviolet rays is restrained in a mold frame 16. A steel ball 17 which is larger by about 20 to 30μ from the previously used steel ball is heated to 200 to 300°C, and is then slowly forced into this film to form the film in hemispherical form, after which it is water-cooled. The mold of this film is fitted to the metal mask 14 and the assembly is held for a short time at temperatures of 150 to 200°C, after which it is cooled. Thereby, the mask body 18 in which the metal mask and film are integrated is obtained.