In a semiconductor laser driving device and method, a first current below an oscillation threshold current of a semiconductor laser is outputted to the laser invariably. A second current needed for light emission of the laser responsive to an input signal is outputted to the laser. A third current for controlling the laser such that a detected amount of emission light from the laser accords with a given value is outputted to the laser. A predetermined auxiliary current is outputted to the laser. An initialization operation is performed to detect luminescence characteristics of the laser, and a signal indicating a value of the second current derived from the detected luminescence characteristics is outputted. The third current is controlled so that an amount of light outputted by the laser receiving a sum of the first, second, third and auxiliary currents, accords with a predetermined amount.