To connect an internal heat exchanger having a double pipe structure to a front side circuit and a rear side circuit while maintaining the double pipe structure.

The double piping joint device 11 has a joint part having a double pipe structure to be joined three ways. An end of a first joint part is connected to an other end of first double piping 41 connected to each of a compressor and a receiver. An end of a second joint part is connected to an other end of double piping 46 and second double piping 43 connected to a front side expansion valve 4. An end of a third joint part is connected to an other end of third double piping 49 connected to a rear side expansion valve 6. The first double piping 41, the double piping joint device 11, the double piping 46, the second double piping 43, and the third double piping 49 configure the internal heat exchanger along with piping.