A method and apparatus for manufacturing an X-ray mask having a mask substrate and a supporting frame, wherein the mask substrate having a first surface on which a mask pattern is provided or to be provided is to be fixed onto a first surface of the supporting frame by using an adhesive material, is disclosed. A first base has a first engaging surface to be opposed to and engageable with the first surface of the mask substrate and a second base has a second engaging surface to be opposed to and engageable with a second surface of the supporting frame on a side thereof remote from the first surface thereof. Attracting device is actable on the first and second bases to attract the mask substrate to the first base and to attract the supporting frame to the second base, respectively, whereby the mask substrate and the supporting frame are held fixed by the first and second bases, respectively. Interval adjusting device relatively moves at least one of the first and second bases to the other with the mask substrate and the supporting frame being held by the first and second bases, respectively, wherein at an adjusted interval the first engaging surface of the first base and the second engaging surface of the second base are held in parallel to each other.