1. A pattern generation method of a design pattern for use in circuit pattern formation, the method comprising: acquiring a design constraint for a first patterns which uses, 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, the first patterns being to be formed on a film by a first process; correcting the design constraint for the first patterns in accordance with pattern conversion by a second process used to form a second pattern on the film on the basis of the arbitrary one of the first patterns, and thereby acquiring a design constraint for the second pattern which uses, as indices, two pattern spaces on both sides of a predetermined pattern of the second pattern, or two patterns on both sides of a predetermined pattern space of the second pattern, the second pattern being to be used to form a circuit pattern on the film in conformity with the design pattern corresponding to the second pattern; judging whether the design pattern fulfils the design constraint for the second pattern; and changing the design pattern so as to correspond to a value allowed by the design constraint in the case where the design constraint is not fulfilled.