A control device mounted on a four-wheel drive vehicle includes: a slip ratio calculating unit that obtains a slip ratio of main driving wheels based at least on wheel speeds; a smoothing unit that smooths the slip ratio by filtering; and a driving force control unit that controls a driving force transmission device so that a driving force that is transmitted to auxiliary driving wheels increases as the slip ratio smoothed by the smoothing unit increases. The smoothing unit uses a larger time constant for the filtering when a vehicle speed is less than a predetermined value than when the vehicle speed is equal to or higher than the predetermined value