Provided are an optical element and a method of producing an optical element in which sufficient adhesion with an upper layer can be secured without damaging spectral characteristics. The production method includes the step of forming a first structural body in which a space part and a structural part are alternately and repeatedly arranged, the step of forming an etching stopper layer on an upper part of the structural part, and the step of forming a second structural body on the etching stopper layer by etching.