At the first etching step of etching an SOI substrate from a first silicon layer side, a portion of a first structure formed of the first silicon layer is formed as a pre-structure having a larger shape than a final shape. At the mask formation step of forming a final mask on a second silicon layer side of the SOI substrate, a first mask corresponding to the final shape of the first structure is formed in the pre-structure. At the second etching step of etching the SOI substrate from the second silicon layer side, the second silicon layer and the pre-structure are, using the first mask, etched to form the final shape of the first structure.