To provide a vehicular hydraulic shock absorber with a reservoir tank mountable even on any kind of vehicle without the need for professional skill.

The vehicular hydraulic shock absorber comprises a lower bracket 4 for fixing a cylinder body 3 to a wheel part, a shell case 5 fitted through the lower bracket 4 and threaded to an inside screw groove, a seat lock 6 threaded to the shell case 5 for positioning the shell case 5 on the lower bracket 4, a piston rod 7 slidably inserted into the shell case 5 along its center axis, and an upper mount 8 fitted through the upper end of the piston rod 7 and slidably attached thereto. The reservoir tank 2 and the shell case 5 of a cylinder body 3 are rotatably attached via a tank adapter 12.