PURPOSE: A radiator manufacturing method is provided to prevent corrosion on the inside of pipelines of a radiator as well as on the radiator body by forming a phosphate chemical conversion coating layer in the pipelines. CONSTITUTION: A radiator manufacturing method comprises the steps of: cutting one set of steel sheets to a predetermined size; degreasing, washing, pickling, and washing the set of steel sheets, and drying the steel sheets with hot air or ultraviolet rays; inserting the set of steel sheets into a roll forming machine to form an embossment; dipping the set of steel sheets in a chamber for 5-10 minutes to form an anodic film of 1-40 g/m^2 on the whole surface of the set of steel sheets; coupling the edges of the steel sheets and spot welding two of the steel sheets into one body; welding a pipe to a radiator body to form a pipeline; injecting high-pressure water into the pipeline of the semi-finished radiator to remove welding slag and dust; charging an aqueous solution into the semi-finished radiator to implement a water pressure test; and moving the semi-finished radiator to a painting line and applying paint to the whole surface of the radiator by dipping, spraying, or electrostatic painting.