A steering damper system for motorcycles provided for generating an adjustable damping force for restraining the shaking of the steering system at the time of disturbance. The system includes a cross member laid between the front portions of the mainframes branching to the left and right from the head pipe and extending to the rear, and a steering damper mounted at the center of the cross member. A sector gear projects forward from the housing, and the teeth thereof are inserted through the opening formed on the head pipe, and are engaged with the drive gear integrally mounted around the steering stem rotatably supported within the head pipe. The resulting steering damper provides the desired adjustable damping force without adversely increasing the inertia of the steering system.