The magnitude of the linear damping coefficient CS is so determined that it decreases as the maximum amplitude value [alpha] of the intermediate frequency spring up acceleration increases. Therefore, when a damping force controller controls/damps the vibration of a spring upper-member by using the nonlinear H[infinite] control theory, and if the maximum amplitude value [alpha] of the intermediate frequency spring up acceleration inputted into a suspension device is small, the linear damping coefficient CS is set to a large value. Consequently, the required damping force Freq is strong, and the vibration of the spring upper-member can be quickly damped. If the maximum amplitude value [alpha] of the intermediate frequency spring up acceleration is large, the linear damping coefficient CS is set to a small value. Consequently, the required damping force Freq is weak. The degradation of the riding comfort of when an intermediate frequency vibration is inputted, especially when the vibration velocity is high can be reduced.