To provide a mobile work vehicle for an overhand installation installed at the tip of a main girder when constructing a bridge by an overhang installation method, which can convey and install a prefabricated package in a lump and is movable along rails installed on the main girder for a shift.

The interval between four studs forming a main frame 6 is made larger than the web width of the main girder 1, and the right and left of the lower end of each of four studs are connected together by a lower cross beam 9. The front and rear of the lower end of each stud are connected together by a connecting beam 25, and wheels 16 and 19 for moving on the rails 10 are fitted to both end sections of front and rear lower end cross beam.