PURPOSE: To enable measurement of weight of a wheel accurately without abverse effect of loading position and thickness of rim by obtaining in advance the relationship between the laterally moved amount by known lateral and vertical pressures and detected strain value as fundamental data.

CONSTITUTION: The laterally moved amount of a wheel 2 is detected with respect to a rail 3 by a laterally moved amount detector 1, and strain caused at the wheel 2 is simultaneously detected by a strain gauge 10 provided at the side surface of the rim 2R of the wheel. Known lateral and vertical pressures are applied to the wheel to thus obtain the relationship between the detected lateral and vertical values and the lateral and vertical pressures as fundamental data. Since the lateral and vertical pressures are calculated on the basis of the fundamental data from the detected values of respective detectors when unknown lateral and vertical pressures are applied to the wheel, accurate weight can be measured always without adverse effect of the loading position and the thikness of the rim of the wheel.