To provide a driving system which achieves high energy saving, improves installability by downsizing hydraulic pumps, and has extensibility enabling an attachment to be easily added, in a working machine.

A system for driving a working machine includes: hydraulic closed circuits 100, 101 that connect hydraulic pumps 2a, 2b to hydraulic actuators 7a, 7b, respectively, in a closed circuit manner; a hydraulic open circuit 102 which connects a hydraulic pump 8a to hydraulic actuators 7c, 10a, 10b in an open circuit manner; first assist circuits 200, 202 that connect between the hydraulic closed circuits 100, 101 so as to cause a hydraulic fluid to be mutually supplied between the hydraulic closed circuits 100, 101; and second assist circuits 201, 203 that connect the hydraulic closed circuits 100, 101 to the hydraulic open circuit 102 so as to cause the hydraulic fluid to be supplied from the hydraulic closed circuits 100, 101 to the hydraulic open circuit 102.