Control system for work machine, and control method for work machine

This control system for a work machine controls a work machine provided with: a traveling device; work equipment which has a work tool; and a rotating body to which the work equipment is mounted, which is mounted on the traveling device, and which rotates relative to the traveling device. The control system for a work machine comprises: a position detection device that detects a first position, which is the position of part of the work machine, and outputs said first position as first position information; a status detection unit that detects and outputs operation information indicating an operation of the work machine; and a processing device that uses said first position information and said operation information to obtain a second position corresponding to the position of the part of the work machine, and uses said second position information to obtain the position of at least a part of the work machine.