Provided is a method for joining piping that makes it possible to simplify a work procedure, prevent deformation of piping, and minimize increases in costs at the time of joining. In the method for joining piping, first piping 1 is joined with second piping 2 that has an end section provided with an expanded pipe section 2a in which the inner diameter is larger than the outer diameter of the first piping 1. A solder joining material 3 is fitted to the first piping 1, the first piping 1 having the solder joining material 3 fitted thereto is fitted into the expanded pipe section 2a of the second piping 2 and the solder joining material 3 is brought into contact with the end surface 2b of the expanded pipe section 2a, and the solder joining material 3 is subsequently heated.