To provide a driving circuit for a gas discharge tube capable of omitting a dedicated power source for preheating a heating heater and greatly simplifying a circuit structure.

This driving circuit D1 used for discharge lighting of a gas discharge tube 101 is provided with a constant current power source 11, a starting circuit 21, and a shunt circuit 31. The starting circuit 21 feeds current to the heating heater 111 from the constant current power source 11 for a fixed time and shuts off the excitation to the heating heater 111 after the lapse of the predetermined time for stopping power supply and includes a timer relay 23. The shunt circuit 31 is connected to the heating heater 111 in parallel after discharge for diverting discharge current in the gas discharge tube 101 and is arranged in serial connection between one end part 111a of the heating heater 111 and a ground terminal 51. The shunt circuit 31 includes a resistor 33 connected in parallel to the heating heater 111 and a relay 35.