PURPOSE: To enhance accuracy at the time of measuring or regulating a traveling unit by a structure wherein an supporting element for wheel plate has a chamber being fed with pressurized liquid on a flat supporting face contiguously to the flat bottom face of the wheel plate.

CONSTITUTION: A supporting element comprises a tubular support 4 being fitted in the hole 5 of a substrate 1 and provided, at the upper end thereof, with an annular flange 6. The supporting element is fed with pressurized water through a connection hole 9 and a wheel plate 3 is lifted to provide a gap with respect to a supporting face 7. The pressurized water passes through the gap and flows from a recess 8 into an annular groove 10. When a pump is operated, the plate 3 is lifted continuously and floated on the liquid. Consequently, a traveling vehicle is fully relaxed and measurement of shape and regulation of the traveling unit can be performed with high accuracy. After finishing introduction of to the pressurized liquid, the plate 3 abuts on the supporting face 7 and the traveling vehicle can ride on the plate 3 or descend therefrom.