PURPOSE: To secure anisotropicity by providing a deformed restricting part only on one side in a two-dimensional direction in a top plan view of an upper surface plate in an air spring provided with a cylindrical flexible body whose upper and lower ends are airtightly connected to the upper surface plate and a lower surface plate.

CONSTITUTION: An upper surface plate 3 and a lower surface plate 10 are provided on upper and lower installation members 1, 2, while upper and lower ends of a cylindrical flexible rubber bellows 12 are connected to an upper surface plate 2 and a lower surface plate 10. Pressure air is supplied from an air supplying projection 6 to obtain an air spring. A deformed restricting part 18 is provided only on one end in a two-dimensional direction in a top plan view of the upper surface plate. The right side is one side of two-dimensional direction, while the left side is the other side perpendicular to the above- mentioned side. Spring characteristics can be sufficiently differed in one side from the other side by means of the deformed restricting part 18, and anisotropicity is secured.