In a shock absorber of the type including a piston-cylinder assembly, a coiled suspension spring and a damping-force control mechanism arranged on the piston, the upper spring seat member is rotatably mounted on the top end of the piston rod and operatively connected with the control mechanism through a sleeve rotatably fitted over the piston rod to serve also as an adjusting dial. The control mechanism includes, among others, an orifice disc formed therein with circumferentially spaced orifices of different diameters and arranged on top of the piston. The orifice disc is rotatable with the sleeve selectively to place the orifices in fluid communication with a fluid passage formed through the piston. The damping characteristic of the shock absorber can be readily adjusted from outside whenever desired by manual operation of the adjusting dial or upper spring seat without the need for dismounting the absorber unit from the vehicle.