Optics-use resin molded body production method, resin fiber production method, and resin fiber production apparatus

This optics-use resin molded body production method comprises: (i) depressurizing the interior of a vessel wherein a molten optics-use resin is being held; (ii) pressurizing the interior of the vessel wherein the molten optics-use resin is being held; and (iii) molding the optics-use resin, which has been removed from the vessel, into a prescribed form. The (i) and (ii) steps are performed alternately at least once. In the (i) step, the time t1 [min] during which the interior of the vessel is depressurized is set in such a manner that the time t1 and the viscosity [mu]1 [Pa.s] of the molten optics-use resin fulfill the relationship: [mu]1/t1 < 200. In the (ii) step, the time t2 [min] during which the interior of the vessel is pressurized is set in such a manner that the time t2 and the viscosity [mu]2 [Pa.s] of the molten optics-use resin fulfill the relationship: [mu]2/t2 < 200. The viscosity [mu]1 represents the viscosity of the optics-use resin under a shear rate of 0.05 s-1, at the temperature inside the