A driving force transmission device is for a four-wheel-drive vehicle based on the two-wheel drive of rear wheels or front wheels. In the case of the two-wheel drive of rear wheels, a multi-disc clutch mechanism controls the driving force distribution to a front wheel output shaft, and a disconnection/connection mechanism selectively disconnects and connects a front wheel differential and a left front wheel drive shaft. In the two-wheel drive of the rear wheels, the dragging torque of the multi-disc clutch mechanism is made smaller than the friction torque of a front wheel driving force transmission section, and the front wheel differential and the left front wheel drive shaft are disconnected by the disconnection/connection mechanism, thereby stopping the rotation of the front wheel driving force transmission section.