Abstract: An interlocking chain unit includes a stepped rod that determines the positions of case plates in a pair and those of guide plates relative to each other. The stepped rod has a small-diameter part that passes through passage holes of the guide plates respectively. The stepped rod has opposite end portions fitting in countersunk holes respectively formed in respective inner surfaces of the case plates. The stepped rod has a large-diameter part with a guide plate side step abutting on a rim of the passage hole of the guide plate, and a case plate side step abutting on a rim of the countersunk hole of the case plate.