To provide a simple structure for lowering manufacturing costs, to easily change layout in the manufacturing process, and to optionally organize the process.

Two conveyer belts 6 are oppositely arranged in parallel with each other so as to form a closed loop line, and a sliding plate 3 having a width as same as an opposite interval between the belts 6 is fit and fixed to a conveyer frame 7. An arc-shaped inside guide rail 1 and an arc-shaped outside guide rail 2 for changing a route of a tray 4 are fit to the plate 3. When the route is changed by an angle of 180° as in the present case, the inside guide rail 1 and the outside guide rail 2 are semicircles of 180°.