To provide a sheet for assembling a mask designed so as to form a mask that is three-dimensional and fits the face by printing a circle on a sheet, stamping the circle out and gluing together at two positions thereof.

The mask fitting the face is formed by printing a circle, a bent chevron, cut-outs corresponding to the eyes, and the like, on a paper or plastic sheet, tucking in an externally folding line and an internally folding line of designated parts of the mask stamped out, forming the nose ridge three-dimensionally by gluing the part below the nose and the cheeks together, and forming a clearance to help respiration in the part below that. By patterning and coloring the mask, it will become a mask for a costume play. Use of a transparent or semitransparent moisture-resistant sheet makes it usable as a protective mask.