In cases when it is determined that a measured yaw angle (ΨL) can be calculated on the basis of the output of a LIDAR (12), a control unit (15) calculates the measured yaw angle (ΨL) as the estimated yaw angle (ΨE), and performs calibration processing on a gyro sensitivity coefficient (A), a gyro offset coefficient (B), a steering angle sensitivity coefficient (C) and a steering angle offset coefficient (D). Meanwhile, in cases when it has been determined that the measured yaw angle (ΨL) cannot be calculated, the control unit (15) calculates a gyro sensor-based yaw rate (Ψ⋅G) on the basis of the steering angle sensitivity coefficient (C) and the steering angle offset coefficient (D) while calculating a steering angle-based yaw rate (Ψ⋅S) on the basis of the steering angle sensitivity coefficient (C) and the steering angle offset coefficient (D), and weights these calculated values in accordance with the degrees of their reliabilities to thereby calculate an estimated yaw rate (Ψ⋅E) for calculating the estimated yaw angle (ΨE).