The opposite inner ends of the said two short pipes (1, 2) are placed in casing coupling (3) with a come-and-go clearance (6) between said inner ends.

The two ends of the said corrugation pipe (7) are connected respectively with the inner ends of the two short pipes to form a seal, and at least one of the ends of casing coupling (3) is free with relative to two short pipes (1, 2).

A contractible joint device for metal conduit (10), includes an inlet short pipe (1), a short outlet pipe (2) and a casing coupling (3).