A pattern generation method includes: acquiring a first design constraint for first patterns to be formed on a process target film by a first process, the first design constraint using, as indices, a pattern width of an arbitrary one of the first patterns, and a space between the arbitrary pattern and a pattern adjacent to the arbitrary pattern; correcting the first design constraint in accordance with pattern conversion by the second process, and thereby acquiring a second design constraint for the second pattern which uses, as indices, two patterns on both sides of a predetermined pattern space of the second pattern; judging whether the design pattern fulfils the second design constraint; and changing the design pattern so as to correspond to a value allowed by the second design constraint when the design constraint is not fulfilled.