1. A photomask formed with main patterns to be transferred to photosensitive material, wherein one or more sub-patterns are formed inside a rectangular region including all of said main patterns therein, and wherein said sub-patterns are arranged in a manner that a part of at least one pattern selected from a group composed of said main patterns and said sub-patterns is included in a prescribed scan target range of a mask pattern defect inspecting apparatus used for inspecting patterns on said photomask at least in said rectangular region.