A manufacturing method of a metal mask for an AMOLED (Active Matrix Organic Light Emitting Diode) comprises the following steps: selecting a conductive substrate; coating the surface of the conductivesubstrate with a layer of a photoresist; enabling the photoresist to form a photoresist pattern that corresponds to an evaporation hole in the metal mask by means of photoetching, wherein the size ofthe photoetched photoresist pattern is greater than a designed size of the evaporation hole of the metal mask; performing electroforming overgrowth on the conductive substrate with the photoresist pattern to ensure that a growth thickness of a metal material is greater than a thickness of the photoresist pattern, wherein the metal material covers the peripheral edge of the photoresist pattern till the size of an opening area that is not covered with the metal material of the photoresist pattern is consistent with the designed size of the evaporation hole of the metal mask; and removing the photoresist that remains on the conductive substrate. According to the manufacturing method, processing forming can be realized only through one-time pattern photoetching and electroforming processes, so that the process is simple and the cost is low. As the metal mask is formed on the conductive substrate with the photoresist pattern through electroforming overgrowth, the precision is higher.