The present invention provides a method of producing a graded refractive index optical element, the method being capable of easily forming a graded refractive index distribution in a desired portion of a glass substrate without the need for a specific treatment atmosphere, and without using a molten salt. More specifically, the present invention provides a method of producing a graded refractive index optical element comprising applying a paste containing a copper compound, an organic resin and an organic solvent to a glass substrate containing an alkali metal component as a glass component, and then performing heat treatment at a temperature below the softening temperature of the glass substrate.