The four-wheel-drive vehicle has a torque transmission device configured to distribute torque transmitted from an engine to a first set of wheels to a second set of wheels. Throttle-opening of the engine is detected. A first torque command which depends on the throttle-opening is obtained. A rotational speed difference between the first set of wheels and the second set of wheels is detected. A second torque command which depends on the rotational speed difference is obtained. The torque transmission device is controlled based on the first and the second torque command so as to transmit the driving force to the second set of wheels according to the throttle-opening and the rotational speed difference. Then, a signal that corresponds to the throttle-opening is monitored. When the signal is judged being abnormal, the first torque command is ignored so that the torque transmission device is controlled based on the second torque command.