A driving circuit supplies a suppression current (I4) which reduces a decrease in a driving current (Idrive) immediately after occurrence of an overshoot at the time of the rise of the driving current (Idrive) to a laser diode (1). The driving circuit draws a suppression current (I5) which reduces an increase in the driving current (Idrive) immediately after occurrence of an undershoot at the time of the fall of the driving current (Idrive) from the driving current (Idrive).