PURPOSE: To prevent the occurrence of mulfunction and to prevent the occurrence of a reverse roll phenomenon which presents itself during shifting to straight running from turning, by a method wherein a flow rate regulating valve is controlled so that a car height is controlled to a set value by means of an electric signal.

CONSTITUTION: A low pressure fluid chamber 3 is formed between an outer cylinder 1 and an inner cylinder 2 which both serve as a cylinder. A high pressure fluid chamber 7 is formed between a partition 4, which is positioned to that the openings at the two ends of the outer and inner cylinders 1 and 2 are closed, and a cover body 1. A 2-position solenoid valve 28, serving as a flow rate control valve, is located in communicating passages 29 and 30 through which the high pressure fluid chamber 7 and the low pressure fluid chamber 3 are intercommunicated, is brought into a shut-off and a communicating condition by means of valve driving signals (a) and (b). A pressure signal P from a pressure sensor 24 of the fluid chamber 7 is compared with ideal pressure signals P10 and P20. When P exceeds the ideal pressure signal, it is decided that a car height is too increased, and a car height is decreased by outputting the valve driving signal (a) so that the 2-position solenoid valve 28 is opened.