To realize a connecting structure of a pipe body having a sealing mechanism capable of stably achieving high sealing performance, with a simple structure and high workability.

Two pipe bodies 12, 14 are connected by a connecting means in a state of being fixed to each other, and the pressure fluid is applied to a working fluid chamber 32 mounted in a seal structure 16 mounted in a state of being externally inserted to cover a connecting part, whereby a seal member 36 is closely adhered to seal the connecting part on an outer peripheral face of the pipe bodies 12, 14 by the action of the applied pressure fluid.