Laser welding device and laser welding method using same

A laser welding device at least comprising:

• a laser oscillator that generates a laser beam;
• an optical fiber that transmits the laser beam generated in the laser oscillator;
• a laser beam emitting head that is attached to an emission end of the optical fiber and emits the laser beam incident from the optical fiber toward a workpiece;
• a manipulator that the laser beam emitting head is attached to and that moves the laser beam emitting head along a predetermined trajectory;
• and
• a controller that controls the laser beam emitting head so as to cause the laser beam to be scanned two-dimensionally or three-dimensionally on a surface of the workpiece,
• wherein the controller controls the laser beam emitting head or the manipulator so as to change a focal position of the laser beam illuminated on the workpiece in accordance with a shape of a welded portion in the workpiece.