To provide an inexpensive pipe mounting structure for a power cylinder, which connects the pipe by a simple structure.

A swelled part 30 swelled in a radial direction R1 of a cylinder tube 9a is integrally formed with the cylinder tube 9a by a single material. The swelled part 30 is provided with first and second surfaces 31, 32 crossing to each other. A first hole 34 penetrating through the swelled part 30 in the radial direction R1 and forming an opening 33 on the first surface 31 is liquid-tightly closed by a plug 37. The pipe 17 is thread-fastened to a second hole 35 branched from a midway part 34a of the first hole 34. A flange 39 of the plug 37 is pressed to an edge part 33a of the opening 33 of the first hole 34 to become a relax-stop of the plug 37.