To detect foreign matter with high accuracy even on a metal mask in which irregular reflection and shadows occur when surface irregularities etc. are irradiated with light from the front.

On the basis of an image of the metal mask 1 by back light 8, the foreign matter reflected as a shadow in a transmitting part is detected by back light slit part inspection processing (step 22) through the use of gray scale dilation and gray scale erosion. On the basis of an image of the metal mask 1 by oblique illumination 7 irradiating from above at an angle, the location of a mask boundary line is recognized by oblique illumination area creation processing (step 24), and divided into a transmitting part and a mask part to detect the foreign matter which causes irregular reflection at each area and shines. On the basis of both illumination from the front of the metal mask 1 by coaxial illumination 4 and an coaxial reflection image reflected at a transmitting part, the foreign matter reflected as a shadow at the transmitting part is detected by coaxial reflection slit part inspection processing (step 28).