To produce a glass cell having no corner which causes the rising of a liquid by capillary phenomenon by transferring the shape of a mold with high accuracy without forming shrinkage even in a case where the space between a bottom-closed cylinder and the mold is large.

A bottom closed cylinder made of an optical material is heated in a heating furnace 9 up to a temperature at which the cylinder can be formed into a desired shape. A roughly square inner mold 4 having no corner is inserted from the opening 1a toward the inside of the heated cylinder, and the heated cylinder is pushed and extended by means of the front end 4a of the inner mold 4 to reduce the space between the cylinder and the inner mold 4. Subsequently, the pressure of the space between the inner face of the extended cylinder and the inner mold 4 is reduced through a suction hole 8 and a hose by a vacuum pump to make the inner face of the cylinder closely contact with the inner mold 4, and this allows the inner face of the cylinder to be formed into the shape of the inner mold 4.