PURPOSE: To prevent in advance the crack of a build-up part, and then to continuously form a defectless build-up layer over a long period, in the case of executing laser building-up to an object to be worked when there is the working surface inclined against an optical axis of a laser beam.

CONSTITUTION: This device provided with a laser oscillating part 21 for oscillating a laser beam 22, an optical device 24 for introducing the laser beam 22 to an object 23 to be worked, and a metallic supply device 26 for supplying built up metallic material powder 25 to the working surface 23a of the object 23 to be worked. The optical device 24 has a condensing part 28 for setting a condensing position of the laser beam 22 to a position being farther than the working surface 23a of the object 23 to be worked. The metallic material supply device 26 has a material supply part 29 for supplying continuously the metallic material powder 25 to the surface of the object 23 to be worked along an optical axis of the laser beam 22.