It is an object to provide a lane departure warning device capable of generating almost no false warning if a driver performs an avoiding operation of a lane departure. The lane departure warning device estimates the steering amount of the own vehicle toward the center of the lane or the amount correlating with this steering amount based on the parameter representing the vehicle behavior such as the steering angle, the yaw rate and the lateral G, thereby detecting the state of the vehicle steering toward the center of the lane when a driver is performing an avoiding operation to avoid the lane departure (quick steering), and determining whether or not the possibility of the vehicle's departure from the lane is high without using the time TLC and its threshold value Ts, but only based on the determination whether or not the distance D1 or D2 from the outer edge of the front wheel to the marking line is less than the threshold value Ds if the driver performs the avoiding operation to avoid the lane departure (quick steering).