A driving device includes: a power source circuit that converts inputted power to a constant voltage or constant current power, and outputs this converted power; a driver circuit that supplies the power outputted by the power source circuit to a load; and a control unit that receives the voltage or current of the power outputted by the power source circuit, calculates a value by multiplying a control gain by a difference of the detected value and a constant target value, and outputs a feedback signal based on this calculated value to the power source circuit, thereby performing feedback control on the power source circuit, the control unit raising the control gain when the voltage or current of the power outputted by the driver circuit is changed.