PURPOSE: To obtain a smooth surface of frosting work to which contamination is not likely to attach and easy to be removed without pollution and at a low cost by heating and fusing a mat surface of a blast-worked glass moulded body at a temperature around its softening point to make the irregularities in the surface almost spherical, and then cooling the surface.

CONSTITUTION: Blast work is applied to a surface of a glass molded body. The glass moulded body is then put in a heating chamber 41 of a heating device 40 from a charging port 42 and put on a table 50. Next the glass moulded body is heated and fused at a temperature around the softening point of this glass moulded body, that is about 770°C, by a heating means 46 so as to make the irregularities in the blast-worked mat surface almost spherical. After that, the glass molded body is taken out from the charging port 42 and cooled in air, so the irregularities in the mat surface are solidified in almost spherical forms, thereby a smooth frosting-worked surface to which contamination is not likely to attach and easy to be removed can be achieved.