An inner tube (2) connected to a vehicle body is inserted such that it is free to extend and contract in an outer tube (1) joined to a vehicle shaft. A partitioning member (3) which divides an internal oil chamber at the end of the inner tube is provided, a damping valve (4) and a bypass passage (3d) parallel to this damping valve (4) are disposed in this partitioning member (3), a control rod (5) which opens and closes the bypass passage (3d) is provided, and an actuator (20) which controls this control rod (5) is provided in the inner tube (2). By operating the control rod (5) via the actuator (20) to open/close the bypass passage (3d), the damping force generated is varied.