To provide a steel pipe set which is made of two or more steel pipes capable of dispensing with a welding operation in a narrow drift section and the like, capable of being easily and firmly connected without being affected by the weather, and capable of being inexpensively manufactured.

A steel pipe set S1 includes first and second steel pipes P1 and P2. The first steel pipe P1 is provided with L-shaped engaging recess-shaped grooves 4 and 4 which each have a peripheral part of one edge worked to have a smaller diameter than other parts and which each have a small-diameter part provided with a first recess 4a in an axial direction from an edge and a second recess 4b almost orthogonal to the first recess 4a. The second steel pipe P2 has an inside diameter almost identical with that of the small-diameter part of the first steel pipe P1, and has protrusive bodies 15 and 15 provided on an inner surface near the one edge.