To provide a drift removing device which enables to remove correctly the drift component of the yaw rate sensor (an angular velocity meter) contained in a behavior detecting sensor.

The drift component contained in the measured angular velocity is detected by filtering the difference value between the estimated angular velocity, which has been gained by multiplying the steering angle and the travelling speed of a vehicle, and the actually measured angular velocity by a angular velocity meter. The drift component contained in the measured angular velocity is also detected by filtering the difference value between the estimated angular velocity, which has been gained by dividing the lateral acceleration by and the travelling speed, and the measured angular velocity. The first way has a high accuracy when travelling at a lower speed, while the second has a high accuracy when travelling at a higher speed. Thus, the both ways are mixed corresponding to the current travelling speed, the drift component is quantified based on the mixed result, and the correct yaw rate is gained by removing the quantified drift component.