To insulate the heat of an optical element forming die and to retain the forming die at all times while obtaining the adequate core accuracy between upper and lower dies without being affected by the temperature in a press forming chamber and die temperature.

Ceramic 8 is interposed between a die holder 4 for holding the optical element forming die 1 and a holding fitting 10 as a holding member for the optical element forming die. The die holder 4, the ceramic 8 and the holding fitting 10 are fixed by utilizing the thermal expansion and contraction effect therebetween in such a manner that the prescribed spacings between the inside and outside diameters thereof at ordinary temperature are maintained and that these spacings are made zero or to a slightly shrinkage fit in a heating stationary state.