To provide an air spring having a plurality of spring properties, wherein a vertical spring constant is selectively changed by an extremely easy and economical means added to an existing air spring.

Between a cylindrical rubber film 1 and a piston 4 for guiding the rolling operation thereof, various kinds of piston caps 5 having different taper angles θ to an elastic deformation axial direction a-b of an outer face 5a of a peripheral wall portion are provided to be fitted/removed downward to/from the piston 4. The vertical spring constant of the air spring 10 can be changed by the selective use and fitting/removal of the various kings of piston caps 5.