ROLL ANGLE CALCULATION DEVICE AND ROLL ANGLE CALCULATION METHOD

In the invention, a provisional static roll angle is calculated using previous values of a yaw angular speed ωy, a pitch angular speed ωp, and a roll angle φ measured by an IMU (300), a yaw angular speed of a gravitational direction axis, and a wheel speed. A riding posture correction value is calculated based on a difference between a first posture angle obtained based on a center of gravity generated by a riding posture and a second posture angle obtained based on a center of gravity of a vehicle, the first posture angle being an angle obtained from a lateral acceleration Ay acting in a lateral direction of the vehicle and an upper-lower acceleration Az acting in a gravity direction of the vehicle. A confirmed static roll angle φs is calculated by correcting the provisional static roll angle with the riding posture correction value. A dynamic roll angle error is estimated based on a difference between the confirmed static roll angle φs and a dynamic roll angle φd.