A device adjusts the rotational damping of a steering device such that the rotational damping varies depending on whether the rotational motion about a steering axis is caused by a force acting on the steering device of the vehicle or a force acting on the part(s) of the vehicle contacting the ground. The flow of hydraulic fluid in the steering damper partly or wholly is adjusted by a main valve unit that is coupled together with both an attaching part and a steering device. The opening area of the main valve unit is determined by a relative motion between the attaching part and the steering device such that the flow of the hydraulic fluid in a direction from and to the respective damping chambers of the steering damper is controlled depending on the cause of the rotational movement.