To provide a damping force adjustment type hydraulic shock absorber which realizes the enhancement of the air venting performance in a clearance between the upper seal case welded on the top end of a communication tube and the outer periphery of the cylinder when a communication tube for forming an one-way flow of oil from a rod side chamber to a reservoir is inserted into the outer periphery of a cylinder.

In a damping force adjustment type hydraulic shock absorber 10, the upper seal case 41 and lower seal case 42 are respectively welded on the top end and bottom end of a communication tube 40 arranged between a cylinder 11 and an outer tube 15 to form a communication passage 43 between the communication tube 40 and cylinder 11. A communication hole 11A for communicating between a rod side chamber 14A and a communication passage 43 is bored closer to the top end of the cylinder 11. The communication passage 43 and a reservoir 16 are connected to each other through the medium of a damping force adjusting valve 50. A small air vent hole 11B is bored in a part surrounded by the upper seal case 41 of the communication tube 40 at the upper part from the communication hole 11A in the cylinder 11.