An X-ray mask having a mask pattern formed from nickel or a material having nickel as a principal component supported on a thin membrane. The X-ray mask has characteristics substantially equal to those of the conventional X-ray mask employing Au as a mask pattern and is much lower in price than the Au-containing mask pattern. In addition, since the X-ray mask can easily be formed by electroless plating, it is possible to form a mask pattern with a higher accuracy than that in case of employing Au alone.