To automatically ensure an effective engagement length of a threaded joint part between an outer shell and an extension bracket in a hydraulic shock absorber by means of a mechanical stop means without a visual check through a mark on the effective engagement length of the threaded joint part.

An outer shell 2 with an external thread 5 in the outer circumferential surface has a pin fitting hole 12 cut in the base end circumference, and an extension bracket 6 with an internal thread 14 formed in the inner circumferential surface to leave in the bottom a play portion 13 of a width corresponding to a mounting adjustment length of a hydraulic shock absorber 1 has a pin passing hole 15 cut through the region of the play portion 13. The extension bracket 6 is screwed for retraction onto the outer shell 2 via the external thread 5 and the internal thread 14 to register the pin passing hole 15 in the extension bracket 6 with the pin fitting hole 12 in the outer shell 2. In this state, a stop pin 16 is fitted in the pin fitting hole 12 in the outer shell 2 via the pin passing hole 15 in the extension bracket 6. The abutment of the stop pin 16 and the inner end of the internal thread 14 of the extension bracket 6 holds a design target value of the effective engagement length between the external thread 5 of the outer shell 2 and the internal thread 14 of the extension bracket 6, and at the same time, prevents dislodgment of the extension bracket 6 from the outer shell 2.