A method for inspecting a photomask is provided, which is applicable for the photomask with a pattern region and a blank region. First, a wafer is performed a photolithography process by the photomask. The wafer includes a plurality of exposure regions, each of which has a component pattern region. Each component pattern region is surrounded by a scribe line region. Each component pattern region corresponds to the pattern region of the photomask, while the scribe line region corresponds to the blank region of the photomask. Afterwards, the scribe line region is divided into a plurality of virtual pattern regions. The virtual pattern regions are processed by an overlap comparison step one by one. As at least one of the virtual pattern regions overlaps the others incompletely, a part of the blank region on the photomask corresponding to the incompletely-overlapping virtual pattern region has a haze.