Suppression of the vertical bending vibration of carbodies has recently become an essential issue to improve the ride comfort of railway vehicles. For suppressing this vibration, the primary suspension damping force control system with variable axle damper is being developed, which can control its damping force continuously by command current to the damping force control valve. This paper reports the results of numerical simulations for running test applying this system to Shinkansen vehicle, and the results of the running test on Sanyo-Shinkansen line using an actual Shinkansen vehicle fitted with newly-developed variable axle dampers. The control algorithm which controls axle dampers is based on skyhook control theory in one case and LQG control theory in another case. The results of both the simulations and the running tests demonstrate that the vertical vibration of the trucks and the carbody decreased. In the running tests in particular, the system reduced the vertical vibration acceleration PSD peak value due to the natural vibration in the first bending mode by almost 20% compared with the case of using conventional passive axle dampers. As the result, the value of ride quality level (Lr) was reduced by about 3 dB or more.