Abstract: A combination of a lower jig (77) set on a stationary base (79) and an upper jig (75) adapted to cooperate with the lower jig to pinch a work (W), hold the work and move along a guide rail (111) between from a work loading section (69) and a laser welding section (71) is replaced by a loader (113) movable on the guide rail, an upper jig clamp (115) provided on the loader and having a jig receiver (119) for a side edge (125) of the upper jig to be placed thereon and a vertically movable member (123) to be moved downward from above the jig receiver to clamp the side edge of the upper jig, an upper jig lift (103) adapted, when the upper jig is released from the upper jig clamp as the vertically movable member is moved upward, to lift the upper jig to render the loader movable together with the upper jig clamp to the work loading section, a jig transfer guide rail (94) normally downwardly spaced from the lower jig and adapted, when the loader is moved together with the upper jig clamp to the work loading section