A manufacturing method for a cylinder head is described. A masking member is attached to a cylinder head material, which followed by a film formation step. The masking member comprises a mask portion to mask the matching surface with the cylinder block, mask portions to mask each of the openings of intake and exhaust ports and a mask portion to mask at least one narrow region sandwiched between openings of two adjacent port holes and has the shortest distance between opening edges of the two adjacent port holes. All Mask portions are coplanar and linked directly to each other.