A normality detector includes a steering angle yaw rate calculator, a first difference calculator, a lateral G yaw rate calculator, a second difference calculator, and a normality determination section. The steering angle yaw rate calculator calculates a steering angle yaw rate. The first difference calculator calculates a first difference which is a difference between the steering angle yaw rate and an actual yaw rate. The lateral G yaw rate calculator calculates a lateral G yaw rate. The second difference calculator calculates a second difference which is a difference between the lateral G yaw rate and the actual yaw rate. The normality determination section determines that the yaw rate detector is in a normal state when the first difference falls within a first predetermined value and the second difference falls within a second predetermined value.