To make the weight of a traveling truck only act on a measuring rail part and perform a precise measurement by attachably and detachably installing a stopper body to the measuring rail part in no contact with a traveling rail part.

The tapered part 13a of a stopper body S is installed at the rear end part of a measuring rail Rb to the rear wheel 11 of a traveling truck T toward its longitudinal central side. The traveling truck T is retreated in a direction P to advance the wheel 11 above the measuring rail part Rb, and further retreated to bring the rear wheel, 11 into contact with the tapered part 13a, so that the further traveling is prevented. Thus, each wheel 11 of the traveling truck T is placed on the substantially longitudinal center part of each measuring rail Rb. The locking pin 14 of the stopper body S is fitted to a corresponding pin hole, so that it is never dropped out by the collision force in the contact of the wheel 11 with the tapered part 13a. Further, since the stopper body S is supported only by the measuring rail Rb, and non-contact with a traveling rail part Ra, the weight of the traveling truck T acts on only the measuring rail part Rb, and a precise weight measurement can be performed.