PURPOSE: To accomplish forming an optical device in good reproducibility and in high productivity by forming a vitreous raw material with both top and bottom forces at a specified speed, stopping the press operation of the forces through a position- variable-type control means and by pressing again in response to glass shrinkage.

CONSTITUTION: A vitreous raw material 12 thicker than a specified wall thickness is put on a holding table 14, and heated to the softening temperature of the raw material by a hot furnace 13 set at a specified temperature on the way of its carrying into a forming chamber 4, and then transferred into a space between top force 7 and bottom force 8 both heated, in advance, to ca. the transition temperature of the raw material. This vitreous raw material 12 is subjected to press molding at a press speed ≥10mm/sec and a pressure 50kg/cm2 by raising the bottom force 8. The raising is stopped when the step part 15 of a press driving shaft 10 comes into contact with a stopper 16 at a specified position, making the raw material 12 a little thicker (ca. +5μm) than the specified thickness. In response to the cooling and solidification of said raw material 12, the stopper descends, and the bottom force 8 then ascends again, thus accomplishing the press molding to the specified wall thickness interlocking with the shrinkage of the raw material 12.