To highly accurately estimate a vehicle attitude, by correcting an offset error of an acceleration sensor with a simpler constitution.

An acceleration sensor detects acceleration generated in a vehicle, and a GPS receiver outputs GPS data based on GPS positioning data. An attitude estimating part calculates an observation value Y (S320), calculate a system matrix φ (S330), makes a prediction calculation of an error covariance value P (S340), calculates Kalman gain K (S350), and calculates the error covariance value (S360), Thus, an offset error is estimated as a state quantity x (S370), and the offset error of the acceleration sensor is updated (S380). The attitude estimating part arithmetically operates a vehicle attitude vector by using the offset error.