PURPOSE: To manufacture a tempered glass product having high smoothness with high productivity without causing grains, crack or breakage by coating a molded glass body with a powder coating material contg. low m.p. glass powder as the principal component at a high temp. and by baking the coating material.

CONSTITUTION: A powder coating material contg. low m.p. glass as the principal component is used. The coating material may be made of only the low m.p. glass. The glass has a coefft. of thermal expansion satisfying relation expressed by the equation (where α1 is the coefft. of thermal expansion of the low m.p. glass, and α2 is the coefft. of thermal expansion of base glass). A molded glass body is coated with said coating material by electrostatic powder coating at a high temp. such as about 300W700°C immediately after molding, and the coating material is baked. It is preferred that the low m.p. glass powder has ≤about 550°C softening temp. and a smaller grain size than the thickness of the resulting film.