To provide a method for adjusting a standard cylinder length such that the standard cylinder length as the cylinder length in the standard time becomes a specific length.

The method of adjusting standard cylinder length including a step of adjusting the standard cylinder length of a cylinder device which is arranged between a vehicle body and a wheel, stores operation liquid and a porous body therein and functions as a colloidal damper, is configured such that a cylinder length when a cylinder pressure P is made the preset standard pressure PH is specified as the standard cylinder length LH, and any one of the volume in the cylinder device, the amount of the operation liquid and the length of a piston rod disposed on the cylinder device is changed so that the standard cylinder length becomes the design length on the basis of a deviation ΔL from the design length LS required on the design of the standard cylinder length. By employing such a configuration, the standard cylinder length can be made the specific length.