To provide a control system of a power storage device for a direct current electric railway, which can cope with both charge and discharge constantly even with one power storage device, can avoid regeneration disablement by the charge, and can suppress the fluctuation of the electric traction voltage by the discharge.

A control part 23 is disposed as a first control part between a voltage monitoring part 21 and power storage device 9. The control part 23 grasps the on-rail state of a train nearby or the like by monitoring the voltage of the electric traction. The control part 23 transmits an operation signal to a power converter 29 in response to the voltage of the electric traction. A control part 25 is disposed as a second control part between the power storage device 9 and power converter 11. A control part 25 grasps the standby charge amount by monitoring the voltage and the like of a power storage medium 27. The control part 25 transmits an operation signal to the power converter 11 in response to the standby charge amount of the power storage medium 27.