A manufacturing method of a mask assembly includes forming a cell mask including masking patterns and a mesh frame including conductive patterns disposed to correspond to the masking patters and disposing the cell mask and the mesh frame on a mask frame. The forming the cell mask and the mesh frame includes forming a polymer layer, a conductive layer, and a hard masking layer, forming a mask pattern layer including etch patterns, and forming the cell mask and the mesh frame using the mask pattern layer.