If a steering damper is fixed to a top bridge, since the steering damper is comparatively heavy and the top bridge is on the steering side, steering inertia increases. An arrangement structure of the steering damper which does not greatly influence the steering inertia has been realized. A rotatable partition wall is provided in a hydraulic chamber of a steering damper to partition the inside into a right hydraulic chamber and a left hydraulic chamber. Both hydraulic chambers are in communication with each other by a liquid passage. A control valve is provided in an intermediate part of the passage and is switched to a lock or a throttle thereby a damping force zero status or a damping force generation status is set.