A four-wheel-drive-vehicle driving force distribution apparatus has an auxiliary transmission mechanism for switching motive power transmitted to an input shaft at least between two levels, a high speed and a low speed, and transmitting the motive power to a main output shaft; a friction clutch for selectively transmitting the motive power of the main output shaft to an auxiliary output shaft; a ball cam mechanism for changing the pressing force of the friction clutch in a non-step manner; and a shift mechanism for shifting the auxiliary transmission mechanism. A clutch control mechanism is provided between a drive member fixed to an output shaft of a motor and a pinion gear and changes the clutch pressing force caused by the ball cam mechanism corresponding to clockwise rotation of the drive member performed by a motor starting from a control starting point. A shift control mechanism is provided between the drive member and a shifting cylindrical cam and alternately repeating switching between a H position and a L position of the auxiliary transmission mechanism in every counterclockwise reciprocating rotation of the drive member performed by the motor starting from the control starting point.