A method of manufacturing a metal mask includes providing a growth substrate with a conductive surface. Then, a cover pattern is formed on the conductive surface, which has at least one opening and an insulated surface touching the conductive surface. Next, using the cover pattern as a mask, a first electroforming is performed to form a mold part on the conductive surface. The mold part fills the opening and has a conductive pattern surface touching the conductive surface. The conductive pattern surface is flush with the insulated surface. After the first electroforming, the growth substrate is removed, while the cover pattern and the mold part are reserved. After removing the growth substrate, a second electroforming is performed to the conductive pattern surface of the mold part to form a metal pattern. Afterwards, the mold part and the cover pattern are removed from the metal pattern.