Abstract: A mask on which the line length of a mask pattern can be determined with great accuracy. Auxiliary patterns used for determining line length are formed near edges of a pattern to be determined. The position of the edges of the pattern to be determined is determined on the basis of the auxiliary patterns and the amount of a shift in the position of the edges of the pattern to be determined from a designed value is determined. By doing so, the line length of the pattern to be determined is found. The auxiliary patterns are formed so that their shape, line length, and positions will not exert an influence upon functions which a circuit pattern formed on a wafer by transferring the pattern to be determined should originally have.