PURPOSE: To simplify all characteristics of dynamic running of a vehicle and especially improve the load-changeover characteristic when running through curves and longitudinal stability of the vehicle by controlling the continuously controllable longitudinal connecting part in the four-wheel drive vehicle according to the speed-dependent characteristic.

CONSTITUTION: A four-wheel drive vehicle 1 is so constructed that a lateral differential device 6 of a main driving shaft 2 is driven through a clutch transmission unit 5, and a differential device 8 of an auxiliary driving shaft 3 is driven through a longitudinal connecting part 7. In this case, a controlled variable is generated to a driving part 14 of a longitudinal connecting part 7 by a control device not shown in Fig. The controlled variable is set to a functional relation to at least one driving amount determined from the speed of wheels 9, 10 of an auxiliary driving shaft 3. In a first low speed region, driving is stopped, and in a second high speed region, the driving amount is started from zero, and increased to a designated controlled variable at a gradually increasing speed. After that, the designated controlled variable is kept in a second speed region or above.