A control device for a four-wheel drive system of a vehicle, the four-wheel drive system including a transfer case configured to distribute a part of drive power generated from a drive source to left and right secondary drive wheels, a differential mechanism coupled to the left and right secondary drive wheels, a propeller shaft that transmits power delivered from the transfer case, to the differential mechanism, a first meshing clutch provided in the transfer case, the first meshing clutch being configured to selectively permit and inhibit power transmission between the drive source and the propeller shaft, and a second meshing clutch configured to selectively permit and inhibit power transmission between the propeller shaft and the differential mechanism, the differential mechanism including a pair of control couplings (22L, 22R) configured to adjust transmission torque transmitted to the left and right secondary drive wheels, one of the first meshing clutch and the second meshing clutch including a synchro mechanism, the control device comprising an electronic control unit configured to, when the four-wheel drive system is switched from a two-wheel drive state in which the first meshing clutch and the second meshing clutch are released to a four-wheel drive state in which the first meshing clutch and the second meshing clutch are engaged during turning of the vehicle synchronize rotation of the one of the first meshing clutch and the second meshing clutch including the synchro mechanism, by means of the synchro mechanism, characterized in that the electronic control unit is further configured to determine the turning direction of the vehicle and synchronize rotation of the other of the first meshing clutch and the second meshing clutch, by selecting one of the pair of control couplings (22L, 22R) which transmits power to one of the left and right secondary drive wheels which provides an outer wheel based on the determined turning direction of the vehicle and controlling coupling torque of the selected one of the control couplings. a transfer case configured to distribute a part of drive power generated from a drive source to left and right secondary drive wheels, a differential mechanism coupled to the left and right secondary drive wheels, a propeller shaft that transmits power delivered from the transfer case, to the differential mechanism, a first meshing clutch provided in the transfer case, the first meshing clutch being configured to selectively permit and inhibit power transmission between the drive source and the propeller shaft, and a second meshing clutch configured to selectively permit and inhibit power transmission between the propeller shaft and the differential mechanism, the differential mechanism including a pair of control couplings (22L, 22R) configured to adjust transmission torque transmitted to the left and right secondary drive wheels, one of the first meshing clutch and the second meshing clutch including a synchro mechanism, an electronic control unit configured to, when the four-wheel drive system is switched from a two-wheel drive state in which the first meshing clutch and the second meshing clutch are released to a four-wheel drive state in which the first meshing clutch and the second meshing clutch are engaged during turning of the vehicle synchronize rotation of the one of the first meshing clutch and the second meshing clutch including the synchro mechanism, by means of the synchro mechanism, characterized in that the electronic control unit is further configured to determine the turning direction of the vehicle and synchronize rotation of the other of the first meshing clutch and the second meshing clutch, by selecting one of the pair of control couplings (22L, 22R) which transmits power to one of the left and right secondary drive wheels which provides an outer wheel based on the determined turning direction of the vehicle and controlling coupling torque of the selected one of the control couplings.