PURPOSE: To avoid reduction in internal pressure of an air spring up to a prescribed value or less, and reliably prevent nonconformity such as damage of a part caused by reduction in internal pressure of the air spring.

CONSTITUTION: A main piston 25 to receive first indicating pressure through a first indicating pressure port 8c is integrally provided in a pressure sensitive member 25 of a control valve 7A used in a car height adjusting device, and a second indicating pressure port 8d to introduce second indicating pressure is arranged in a valve housing 8, and a sub-piston 29 to energize the pressure sensitive member 25 in the direction for pressing a supply-discharge valve body 21 by an exhaust air cutoff valve body 28 is arranged between the second indicating pressure port and the main piston 25. Therefore, the second indicating pressure is set in the magnitude by which the exhaust air cutoff valve body 28 holds an exhaust air cutoff condition when pressure on the output port 8b side connected to an air spring is reduced to a prescribed value or less.