A method for manufacturing a radiator including preparing, aligning, punching, bending, shearing and riveting, rotating, and removing processes is provided. The shearing, riveting, and rotating processes are repeated. A sheet metal is continuously punched to form a plurality of heat dissipation fins in a manufacturing machine, the heat dissipation fins are then orderly sheared, inserted into the metal base, and further fixed with the metal base by two-direction riveting. The radiator can thus be obtained in an automatic and faster process without unnecessary assembling steps with higher yield and reduced costs.