There is formed, on a stack formed by alternately stacking an oxide film and a nitride film or an oxide film and a polysilicon film on a substrate, a hard mask in which two or more kinds of lines made of mutually different materials are arranged in order. Then, a photoresist is applied onto the hard mask. Furthermore, the photoresist is trimmed until one line is exposed from the end of the hard mask. Moreover, one line of the hard mask exposed beneath the photoresist is etched. Furthermore, a part of the stack exposed beneath the hard mask is etched. The etching of the photoresist, the hard mask, and the stack is repeated while changing etching conditions.