To reduce machining time by shortening the boring length of an elongation side port and a pressure side port in a piston structuring a hydraulic shock absorber.

In a molding step of the piston 105 by a metal mold, annular opening windows 105C, 105D are formed at an outlet end of hydraulic fluid, and introducing holes 105E, 105F of optional length which communicate to the opening windows and are parallel to an axis of the piston are formed. Then, while positioning to the introducing holes, inlet side ports 105A, 105B having a smaller passage area than introducing holes are bored by drilling to communicate to the introducing holes, and the elongation side port P1 and the pressure side port P2 are respectively composed of the opening windows 105C, 105D, the introducing holes 105E, 105F, and the inlet side ports 105A, 105B.