In laser welding, the heat input per unit length is determined by the welding speed and the laser output power. Along with these parameters, there are several other important parameters such as the shielding gas composition, shielding gas flow rate, beam angle, defocusing distance, and so forth. In this paper, the effect of each process parameter on the welding quality was investigated to establish a laser lap welding process for Al sheets. Al 5J32 and Al 6K32 sheets were used as the base metal, and a 4kW disk laser was used as a high brightness laser power source. The bead appearance, the cross-sectional bead shape, X-ray images, and the weight of spatters were examined to evaluate the welding quality.