To provide a method of manufacturing a mask capable of shortening a TAT of a mask manufacturing process and reducing the cost of the mask, to improve a mask manufacturing process, and to provide a semiconductor device manufacturing method which is capable of reducing the manufacturing cost of a semiconductor device.

When a pattern defect D is detected in a first original mask 10-1, a second original mask having only a pattern region containing a defective part is formed through a direct drawing method where an electron beam is used. A region containing the defective part D of the first original mask 10-1 is shielded with a covering film 16 to serve as a shielded region, and a pattern excluding the shielded region of the first original mask 10-1 and the pattern possessed by the second original mask are transferred respectively onto a mask member in an equal-size exposure manner to obtain a slave mask.