To provide an on-vehicle damper controlling system regulating a stroke quantity of an on-vehicle damper by heating and vaporizing a low-boiling point liquid sealed inside the on-vehicle damper and controlling the temperature inside the on-vehicle damper for preventing the empty damper from being heated.

The on-vehicle damper controlling system is provided with the on-vehicle damper 1 and an electric heater controlling system 31 having a voltage controlling circuit 32 and a breaking circuit 33. The on-vehicle damper 1 is charged with the low boiling point liquid BT, and an electric heater 25 is installed so as to be immersed in the low boiling point liquid BT. The voltage controlling circuit 32 controls voltage impressed to the electric heater 25, while the breaking circuit 33 shuts off the passage of electric current to the electric heater 25 when a resistance value R of the electric heater 25 exceeds a predetermined value.