To avoid the danger of derailment and prevent the wasteful consumption of air by selectively operating each lock mechanism according to a plurality of modes determined by the combination of the detection instruction corresponding to each regulating valve changed according to the traveling state of a rolling stock.

A lock mechanism for blocking orifices 14a, 14b to stop the operation of a height regulating valve 4 is constituted by an air passage 36, air pistons 34a, 34b, and blocking rod parts 38a, 38b. The torsional state of a truck is detected from the operating state of a limit switch as the detection device added to the height regulating valve 4, and when the torsion is detected, the lock mechanism consisting of a solenoid valve 37, the air passage 36, the air pistons 34a, 34b and the like is selectively operated to stop the operation of the corresponding height regulating valve 4. According to this structure, a preferable device never increasing the load of a compressor for supplying compressed air even at the time of passing a gentle curve or having no danger of derailment can be provided.