Bias values of pitch axis and roll axis angular velocity sensors in a stationary state where a reference yaw axis of a two-wheeled inverted pendulum vehicle body is stationary in parallel with a vertical direction are acquired. Bias values of the pitch axis and roll axis angular velocity sensors in a turning state where a two-wheeled inverted pendulum vehicle is turned at a predetermined turning angular velocity in a state where the reference yaw axis of the two-wheeled inverted pendulum vehicle body remains parallel to the vertical direction are acquired. Mounting angle errors of the pitch axis and roll axis angular velocity sensors with respect to the two-wheeled inverted pendulum vehicle body are estimated on the basis of the bias values of the sensors in the stationary state, the bias values of the sensors in the turning state and the predetermined turning angular velocity.