A mask inspecting apparatus and method of inspecting a mask having a plurality of openings used in deposition in a desired pattern, the mask inspecting apparatus capable of detecting a defect of the mask through the openings of the mask. The mask inspecting apparatus includes: a detection unit detecting boundary line of each of the openings of the mask; a storage unit storing information about a member on which deposition is to be performed using the mask; a setting unit setting a first boundary line, a second boundary line, and a safety area for each of the openings using the stored information about the member on which deposition is to be performed, wherein the first boundary line forms an outline of a deposition area, the second boundary line surrounds the first boundary, and the safety area is interposed between the first boundary line and the second boundary line; and a control unit determining whether the boundary line of the mask detected by the detection unit does not contact the first boundary line and the second boundary line and whether it is present in the safety area.