To provide a semiconductor device manufacturing method, capable of surely connecting the divided patterns together, lessening a width change in a line at a joint between the transferred patterns, when the divided patterns are formed on a mask and then transferred to a resist for the formation of the pattern of a semiconductor device.

This manufacturing method comprises a first process of forming a first mask, in which a tapered projection getting gradually thinner in width toward its tip, is provided to the connecting edge of a first pattern out of the adjacent divided patterns, and the length of the projection is set 1 to 5 times as long as the width of the pattern (a), a second process of forming a second mask, in which a recessed part complementary in shape to the projection of the first pattern, is provided to the connecting edge of a second pattern out of the adjacent divided patterns, and the length of the recessed part is set 1 to 5 times as long as the width of the pattern (b), and a third process of transferring the first and second pattern to a resist, combining the projection of the first pattern and recessed part of the second pattern together by the use of the first and second mask (c).