To inexpensively manufacture an optical element having excellent environmental resistance, reliability and long-term stability and to increase a filling factor.

A method of manufacturing the optical element made of inorganic material having sub-wavelength structure includes: a process (A) of forming a resin layer whose shape can be transferred on a substrate surface; a process (B) including a step of pressing a mold 24 having the same structure as the sub-wavelength structure to the resin layer to transfer a sub-wavelength structure, which is inversion of the sub-wavelength structure of the mold, to the resin layer to form a sub-wavelength structure made of resin having a projecting part corresponding to a recess of the sub-wavelength structure of the mold on the substrate surface; a process (C) of applying inorganic or organic and inorganic compound sol-gel material having a viscosity of 200 mPa s or less to the surface, thereby filling the recess of the sub-wavelength structure made of resin, and subsequently curing the coated sol-gel material; and a process (D) of removing the resin from the substrate surface, and leaving the sub-wavelength structure made of cured sol-gel material on the substrate surface.