PURPOSE: To spread a spring constant setting area so as to improve air spring performance by arranging a main air spring chamber and a sub air spring chamber at the outer circumference of a damper and freely communicating the sub air spring chamber to the open air via a free openable valve.

CONSTITUTION: A main air spring chamber 3 and a sub air spring chamber 4 are arranged at the outer circumference of a contractible damper 2 in a way that the main air spring chamber 3 is upwards. The upper end of the main air spring chamber is fitted to a car body via mount rubber 5a and an upper mount 5, the rod 2a of the damper 2 is fitted to an upper mount 5 and the lower end of the damper 2 is fitted to a lower mount, so as to construct an air suspension. An opening and closing valve 8 is provided at the sub air spring chamber 4 to be freely communicated to the outside air. It becomes possible to operate only the main air spring chamber or to operate the main and sub air spring chambers separately and simultaneously so that a spring constant setting area is widened to be able to improve air spring performance.