To provide a method for manufacturing a precursor lens for a spherical lens by which thickness in processing to the spherical lens can be made thin while a rim of the precursor lens is not missing and rim thickness is sufficiently maintained.

In a method for manufacturing a precursor lens having a circular outside shape to be processed to a spherical lens, the precursor lens is produced by inputting processing data including frame shape data and rim thickness data of the spherical lens and processing a material block based on the processing data in a processing data input step. At this time, if rim thickness of the produced precursor lens becomes smaller than prescribed thickness based on the processing data of the spherical lens, a spherical lens portion is processed by reflecting the processing data and the rim thickness of the precursor lens is assured by changing an amount of sag in the circumferential portion of the spherical lens portion.