To allow accurate damping force control to be performed in a damping force adjusting type shock absorber with consideration for a lateral force acting on a piston rod.

By a controller C, a real-time control is carried out on a damping force by supplying a control current to a solenoid 7 of a damping force adjusting mechanism 6 of a damping force adjusting type shock absorber 1 in accordance with the traveling state of a vehicle, based on detection signals of various sensors, and thereby enhancing the steering stability and riding quality of the vehicle. A strain sensor 19 is mounted on a piston rod 5 of the damping force adjusting type shock absorber 1. By the controller C, a lateral force acting on the piston rod 5 is computed based on a detection signal of the strain sensor 19, the control current applied to the solenoid 7 is corrected based on a frictional force, between the piston rod and a rod guide, generated by the lateral force, and thereby accurate damping force control is performed.