The present invention provides an optical element which can reliably acquire a difference of refractive indices between a member under a photonic crystal layer and the crystal layer without using such a stacking technique as in conventional processes; a method for manufacturing the optical element; and a semiconductor laser device with the use of the optical element. The optical element has the first layer 500 and the second layer 400 formed on a substrate 100, wherein the second layer includes pores and has a refractive-index periodically changing structure in which a refractive index periodically changes in an in-plane direction; and the first layer has an oxidized region with a lower refractive index than the refractive index of the second layer, in a lower side of the pores of the second layer.