The present lane departure prevention system comprises a position detector means for detecting positional information of a vehicle with respect to a lane of travel, a determining unit for comparing the positional information with a first threshold value indicating a predetermined positional relation with respect to the lane of travel, and determining a departure of the vehicle from the lane of travel on the basis of the comparison result, and a yaw moment applying unit for applying a yaw moment to the vehicle and switching a first process of applying the yaw moment to the vehicle only by steering wheels and a second process of applying the yaw moment to the vehicle by steering the wheels and applying a braking power to the wheels, on the basis of a traveling condition of the vehicle, when the determining unit determines that the vehicle departs from the lane of travel.