PURPOSE: To enhance the accuracy of a lens shape and the yield by a method wherein a resin passage is separated into plural resin passages so that the flow velocity, pressure and charge amount of a molten resin charged into two cavities formed between a lens blank and lining pieces can be controlled independently.

CONSTITUTION: The cavities 3a, 4a and the resin passages connected respectively to the cavities are provided independently so that the flw velocity, pressure and charge amount of the resin charged into the cavities can be controlled independently. Then, the molten resin is injected into the cavitites 3a, 4a through the respective passages. In this case, since the amount of the resin charged into each of the cavities is set, the charge amount is always balanced. The new resin layers produced after charging the resin into the cavities are pressurized by using seperate hydraulic mechanisms provided for the lining pieces 3 and 4, respectively. Accordingly, since the resin passage is split and the flow velocity, charge amount and the like of the resin can be controlled independently for each cavity, a plastic lens excellent in accuracy of shape can be obtained.