LASER WELDING METHOD AND LASER WELDING DEVICE

[PROBLEM] To improve welding quality by making it possible to form protrusions having suitable protrusion heights without being limited by the plate thickness of metal members. [SOLUTION] In a laser welding method, first, a front surface 21a (one side surface) of a first metal member 21 (one metal member) is irradiated with laser light 51, forming a protruding portion 24 on a back surface 21b (other side surface on the opposite side) projecting from the back surface. Next, melting a part of the protruding portion that was formed by scanning laser light to generate a metal melt flow toward a top of the protruding portion, and forming a protrusion 25 projecting higher than the height of the protruding portion 24 from the back surface 21b. Then, the first metal member in which the protrusion is formed is placed in a state of superposition onto a second metal member 22 (other metal member) with the protrusion interposed therebetween, and the portion where the plurality of metal members are superposed is irradiated with laser light and the plurality of metal members are welded to each other.