PURPOSE: To shorten molding cycle and to improve the productivity of disks by providing a temperature regulating groove on the side in contact with the ceramic sintered object of a back plate.

CONSTITUTION: The back plate 6 of a mold is composed of a metal such as steel or carbide material, and is formed into a doughnut shape. A temperature regulating groove 8 is formed on the side of the surface 6d of this back plate 6 in contact with a ceramic sintered object 7. This temperature regulating groove 8 is closed and fixed by the ceramic sintered object 7 lapped on the upper surface 6d of the back plate 6. Since the temperature regulating groove 8 is provided, the ceramic sintered object 7 itself forming cavity-surface 2a may be directly cooled, whereby the cavity may be effectively cooled. Since the temperature regulating groove 8 is provided on the metallic back plate 6, the working of the temperature regulating groove is easy.