A method is provided, of manufacturing a material to be etched that can more preferably prevent a region to be etched from remaining as an un-etched region and reduce deviation of etched/un-etched regions. Patterning (a method of manufacturing a material to be etched) of a substrate 100, which is manufactured by performing etching through an opened region 10 by an etching mask M1, is performed by a first etching process and a second etching process that is performed after the first etching process. The second etching process is a process for etching a region including a region that is not etched by the first etching process. An un-etched region, which is the same as etched using a virtual etching mask M1′, is formed on the surface of an object to be etched by the first and second etching processes.