A driving system includes an engine, a motor generator, an output unit, a power transmission mechanism, and a controller. The output unit outputs at least one of an engine driving force generated by the engine or a motor driving force generated by the motor generator. The power transmission mechanism selects a first drive mode in which both of the engine driving force and the motor driving force are transmitted to the output unit, and a second drive mode in which only the engine driving force is transmitted to the output unit. The controller controls the power transmission mechanism to select the first drive mode when a first fuel consumption rate of the engine in the first drive mode is or is estimated to be lower than a second fuel consumption rate of the engine in the second drive mode.