PURPOSE: To drastically simplify the photomask manufacturing process and to provide an inexpensive photomask by doping the whole surface of the glass substrate with metal impurities, thereafter irradiating the desired region of the glass substrate with a X-ray beam and forming a light shielding pattern by coloring the metal impurities in the region irradiated with the X-ray beam.

CONSTITUTION: The one surface of the glass substrate 1 is doped with the metal impurities 2 (e.g. aluminum, Fe, etc.) by using the ion implantation method, etc. Thereafter the glass substrate 1 is heated to thermally diffuse the metal impurities 2 into the glass substrate 1. The doping amount of the metal impurities 2 of some ppm level is sufficient for the purpose, and the doping amount of such level does not adversely affect the transmissivity of the glass substrate 1. Then the desired region of the glass substrate 1 is irradiated with the X-ray beam XB cnverged the diameter to a prescribed value. At this time the metal impurities 2 irradiated with the X-ray beam XB is colored by the X ray energy. Therefore the light shielding pattern 3 consisting of the colored metal impurities 2 is formed in the region irradiated with the X-ray beam XB.