A shaft rotating device for rotating a shaft of a medical instrument about its longitudinal axis relative to a handle of the medical instrument comprises an operating element for rotating the shaft. The operating element is arranged at a proximal portion of the shaft and it is in driving connection with the shaft such that the shaft is rotatable relative to the handle against frictional forces. The shaft rotating device further comprises a frictional element with a surface. The surface of the frictional element is in frictional contact with the surface of a counterpart for keeping the shaft and the handle rotationally stationary with respect to each other and movable against the frictional forces. The operating element and the frictional element are in operational connection with respect to one another such that a torque applied to the operating element decreases the frictional forces. The shaft and the frictional element are in operational connection with one another such that a torque applied to a distal portion of the shaft increases the frictional forces.
