The invention provides a laser welding device for relieving the quality difference of welding lines and a welding process of the laser welding device. The laser welding device and the welding process can effectively eliminate the quality difference, caused by the difference of welding base metal, the difference of welding focus positions, the difference of protection gas flow amounts, the difference of welding exhaust flow amounts and the like, of welding lines. The laser welding device comprises a laser generator connected with a controller, an infrared temperature sensor is further connected to the controller, the laser generator is in transmission connection with a laser coupler, the laser coupler passes through a beam expanding lens and a focusing lens and then is focused on a welding workpiece, and the infrared temperature sensor is arranged at the focusing point close to the welding workpiece.