The recording layer (to-be-etched layer), a main mask layer, and a sub mask layer are formed in this order over a substrate, and the sub mask layer is processed into a predetermined concavo-convex pattern. Next, parts of the main mask layer under the concave portions are removed by reactive ion etching using oxygen or ozone as the reactive gas. Parts of the recording layer under the concave portions are also removed by dry etching, whereby the recording layer is shaped into the concavo-convex pattern. The main mask layer is chiefly made of carbon. The sub mask layer is made of a material having an etching rate lower than that of carbon with respect to the reactive ion etching in the step of processing the main mask layer.