The present invention relates to an apparatus and a method for lap-welding metal sheets. The apparatus for lap-welding metal sheets directs a burr of an upper sheet among metal sheets which are lap-welded to a direction opposite to an overlapping direction to weld the metal sheets. The direction of the burr created while cutting the metal sheets is directed to the opposite side of the overlapping direction to prevent a gap by the height of the burr to prevent a welding defect such as a gas hole.
