To completely prevent a dropped foreign matter from attached to a conveyed product by comprising a pair of first covers for covering a product conveyed by a first chain conveyor and a pair of second covers for covering a product conveyed by a second chain conveyor.

A printed wiring board 9 is vertically suspended by deforming a supporting rod 4 and loading a top plate 3 of a hanger 8 comprising a C- shaped curved portion 5 at an angle of 45 degree to the transporting direction 11 on a pair of chains 2a, 2b forming a first chain conveyor 1. Then the printed wiring board 9 is covered by a pair of first covers 10a, 10b horizontally mounted in such manner that they are wrapped one another through the C-shaped curved portion 5, and automatically conveyed. The printed wiring board 9 is vertically suspended by loading the top plate 3 on a pair of chains forming a second chain conveyor, and automatically conveyed in a state that it is covered by a pair of second covers in a state that an angle of the curved portion 5 to the transporting direction is 45 degrees.