To solve a problem of the part of a bypass section incapable of being used in a type where various operations are conducted for an article by a working device as a working section, because two expandable means are required for prevention of a chain from being loosened in adjusting the length of the bypass section for an article conveying route, only one expandable means is impossible to use, and the length in the depth direction of the bypath section is constituted so as to be expanded or contracted.

A drive device 40 is driven positively, both movable frames 20, 30 are made to approach each other, and the length of a protruding route part 10A is decreased for adjustment, thus decreasing working time. Both the movable frames 20, 30 are operated, separated from each other, and the length of the protruding route part 10A is increased for longer working time. The route length is changed in the direction along an article conveying route 10, and a group A of articles are always made to face a working device 12 at the protruding route part 10A. By disposing guide wheels 22, 23, 32, 33, it is possible to prevent a driving chain 2 from being loosened and always provide smooth adjustment of the route length.