PURPOSE: To efficiently and safely carry out roofing work by temporarily loading materials and a worker on a working device that can be moved on the roof structural members built nearly in the horizontal direction as rails, and by moving it from to the one side of the roof to the other side thereof.

CONSTITUTION: A working device 1 is made up of a frame 2, structural members 9, rolling rollers 5, guide rollers 6, and wire ropes. The working device 1 is placed on the one end 20X of a roof, and a worker temporarily loads materials on the loading surfaces 4a of a stepped loading body 4, and also the worker himself gets on the loading body. Then, the worker takes hold of a flexible wire 7 and pulls it for moving the device 1 from the end 20X of the roof to the other end 20Y, and stops it as the occasion may demand for carrying out the bolt tightening work, painting work, bed plate sticking work or roofing- paper and roofing-material sticking work. Thus, work load can be reduced, and expenses can be saved, and also the enhancement in work efficiency and safety can be secured.