A four-wheel drive vehicle comprising clutch control device, - wherein in the four-wheel drive vehicle of the left and right front wheels (6, 7) and the left and right rear wheels (19, 20), one pair is set as the main drive wheels (6, 7) which are connected to a drive source and the other pair is set as the auxiliary drive wheels (19, 20) which are connected to the drive source via a clutch (8, 16), - the clutch control device comprising plural clutches (8, 16), that is, a dog clutch and a friction clutch, that are respectively arranged separately in a drive branch-side transmission system path and in an auxiliary drive wheel-side transmission system path which sandwich a differential, of a system for transmitting drive force to the auxiliary drive wheels (19, 20), - wherein: - the dog clutch is configured to separate the system for transmitting drive force to the auxiliary drive wheels (19, 20) from the system for transmitting drive force to the main drive wheels (6, 7) by releasing the clutch, and - the friction clutch is configured to allocate a portion of the drive force from the drive source to the auxiliary drive wheels (19, 20) in accordance with a clutch engagement capacity, and - the clutch control device comprising a clutch control unit as a clutch control means which is configured to carry out an engagement and disengagement control of the dog clutch and an engagement and disengagement control of the friction clutch in accordance with a vehicle state that is detected by a vehicle state detection device (35, 36), and which can switch between a disconnected, two-wheel drive mode in which the two clutches (8, 16) are disengaged and a connected, four-wheel drive mode in which the two clutches (8, 16) are engaged, characterized in that the clutch control unit is provided with a synchronization speed control unit that is configured to reduce a synchronization speed of the dog clutch more during vehicle deceleration than when the vehicle is not decelerating at a time of transition from the disconnected, two-wheel drive mode to the connected, four-wheel drive mode. - wherein in the four-wheel drive vehicle of the left and right front wheels (6, 7) and the left and right rear wheels (19, 20), one pair is set as the main drive wheels (6, 7) which are connected to a drive source and the other pair is set as the auxiliary drive wheels (19, 20) which are connected to the drive source via a clutch (8, 16), - the clutch control device comprising plural clutches (8, 16), that is, a dog clutch and a friction clutch, that are respectively arranged separately in a drive branch-side transmission system path and in an auxiliary drive wheel-side transmission system path which sandwich a differential, of a system for transmitting drive force to the auxiliary drive wheels (19, 20), - wherein: - the dog clutch is configured to separate the system for transmitting drive force to the auxiliary drive wheels (19, 20) from the system for transmitting drive force to the main drive wheels (6, 7) by releasing the clutch, and - the friction clutch is configured to allocate a portion of the drive force from the drive source to the auxiliary drive wheels (19, 20) in accordance with a clutch engagement capacity, and - the dog clutch is configured to separate the system for transmitting drive force to the auxiliary drive wheels (19, 20) from the system for transmitting drive force to the main drive wheels (6, 7) by releasing the clutch, and - the friction clutch is configured to allocate a portion of the drive force from the drive source to the auxiliary drive wheels (19, 20) in accordance with a clutch engagement capacity, and - the clutch control device comprising a clutch control unit as a clutch control means which is configured to carry out an engagement and disengagement control of the dog clutch and an engagement and disengagement control of the friction clutch in accordance with a vehicle state that is detected by a vehicle state detection device (35, 36), and which can switch between a disconnected, two-wheel drive mode in which the two clutches (8, 16) are disengaged and a connected, four-wheel drive mode in which the two clutches (8, 16) are engaged,