To provide a manufacturing method of a spool which improves abrasion resistance of the spool to be manufactured.

The spool cut in a cutting process 1 is polished in a polish process 2 and soaked in an electrolytic solution to be given anodizing processing in an anodizing filming process 3 so as to form a porous anodizing film on the surface of the spool. This spool is washed with water in a water-washing process 4, and oil is applied or the spool is soaked in oil in an oil applying process 5. And in a control valve assembling process 6, the spool is assembled to a valve body of a control valve, and this control valve is assembled to an automatic transmission in an AT unit assembling process 7 and assembled to a vehicle in a vehicle assembling process 8.