PURPOSE: To obtain high measurement precision by calculating the actual tire steering angle and the actual camber angle by measuring the rotary stream line direction and the wheel travel quantity of the tire tread at two places or more in the measurement of the wheel alignment variation quantity during traveling.

CONSTITUTION: A tire tread part is measured from the car body coordinates X-axis and Z-axis, having the center of the tire as original point. Vector sensors 101 and 105 for X-axis and Z-axis as rotary stream line measuring means and a laser displacement meter 107 as a wheel traveling quantity measuring means which measures the displacement of a suspension arm are provided. The actual steering angle δ is calculated by a steering angle correcting circuit 202 from the steering radius (r) as the coefficient set by a steering radius setting circuit 201, measured steering angle α and the camber angle γ. Further, the actual camber angle γ is calculated by a camber angle correcting circuit 204 from the tire radius R as the coefficient set by a tire radius setting circuit 203, measured camber angle β, wheel traveling quantity H, and the steering angle δ.