Laser stitch welding device and welding method therefor

A laser stitch welding device, comprising: a laser welding assembly ( 3 ) configured to release laser beams from a front surface onto plates ( 5 ) to be welded that are stacked; a pressing piece ( 2 ) for adjusting a spacing between the stacked plates; detecting assembly for detecting a welding parameter of the stacked plates from a back surface; and a controller ( 1 ) for adjusting in real time the pressing level of the pressing piece ( 2 ) and/or operation parameters of the laser welding assembly ( 3 ) based on the welding parameter detected by the detecting assembly. The laser stitch welding device is capable of detecting in real time welding parameters such as back surface temperature and thermal infrared image of welding seams ( 6 ) when welding the plates. A control system controls the pressing level of the pressing piece or the operation parameters of the laser welding assembly based on the welding parameters to adjust the welding in a timely manner, thus achieving adaptive and stable control of weld penetration. The present application further provides a welding method for the laser stitch welding device.