To provide a semiconductor laser drive device, where a bias current is corrected in a short time with no change in the bias current at adjustment.

A bias current with a prescribed value and a drive current changing according to an image are allowed to flow in a semiconductor laser, while its light-emitting amount is controlled. Here, with a bias current VD is kept constant, a drive current VD is changed so that the light-emitting amount of a semiconductor laser VD is adjusted to set light-emitting amounts VG1 and VG2. Detected values CA and CB corresponding to the drive current at adjustment are stored in a CPU 10. Based on the plural detected values CA and CB acquired for preset different light-emitting amounts, a set variable corresponding to the bias current after correction is acquired. Based on the acquired set variable, a set data BS is outputted to redo setting of the bias current.