A driving force control system for improving energy efficiency under a motor-drive mode. The control system selects the motor-drive mode from a single motor-mode where a vehicle is powered by any one of the rotary devices, and a dual motor-mode where the vehicle is powered by both rotary devices. The driving force control system is configured to select the single-motor mode rather than the dual-motor mode, provided that an increment of an energy consumption to establish the dual-motor mode is larger than a decrement of the energy consumption to be achieved by the dual-moor mode, under a driving condition where a required driving force can be achieved by either the single-motor mode or the dual-motor mode.