A position controlling device in a lens system with a variable focal length with high-precision focusing having a small amount of required recorded information, even when there are large number of divisions of the object distance and of the focal length includes a distance measuring device that detects the object position and transmits photographic distance information. A detecting device detects the movement amount from a standard position of the movable lens group of the lens system when the focal length of the lens system changes. A calculating device calculates the required movement of the focusing lens unit of the lens system, based on the photographic distance information and the movement amount of the movable lens unit. Finally, a controlling device drives the focusing lens unit and performs focusing, based on the required movement calculated by the calculating device. The movable lens unit moves monotonically to the object side or to an image side when the focal length of the lens system is changed. In this manner, the focusing movement required increases monotonically and gradually when the focal length of the lens system changes from the wide-angle end to the telephoto end for a given photographic distance.