PURPOSE: To enable the detection of a correct angular velocity signal, by using a vibration type angular velocity sensor for the detection of angular velocity while a bearing sensor relying on earth magnetism is arranged to be a comparison sensor for angular velocity zero to remove noise due to vibration or a zero-point drift due to temperature change.

CONSTITUTION: An angular velocity signal of a vibration type angular velocity sensor 1 and a signal of an earth magnetism sensor 2 converted into an angular velocity signal through a differentiation circuit 3 -- these two signals are compared with a comparator 4, the reference of zero-point is determined with the earth sensor 2 and the measurement of the angular velocity is done with a piezo-electric vibration type angular velocity sensor 1 or rate gyro. Here, even if the output of the piezo-electric vibration type angular velocity sensor 1 is produced due to a noise other than the angular velocity, the output is identified as noise as long as the differentiation output of the earth magnetism sensor 2 is zero and hence, angular conversion will not be executed. On the other hand, the angular conversion is executed based on the output of the piezo-electric type angular velocity sensor 1 only when the earth magnetism sensor 2 and the vibration type angular velocity sensor 1 both produce angular velocity outputs. Thus, a correct bearing can be determined.