To provide a pipe fitting structure of a power cylinder, which has fewer components and reduces the labor required for the assembly, and also to provide a vehicular steering device using the same.

A swollen part 24 formed of a single material and integrated with a cylinder tube 9a is provided. A first hole 28 of the swollen part 24 extends in the radial direction R of the cylinder tube 9a and is communicated with an oil chamber 15, and an opening 27 is formed in a first surface 25 of the swollen part 24. A second hole 30 of the swollen part 24 extends from a middle portion 28a of a first hole 28 across the first hole 28 with a pipe 17 being connected thereto. A fixing member 35 formed of a sheet metal to fix the pipe 17 to the swollen part 24 has: a closed area 38 to close the opening 27; an edge part 40a of a groove 40 to be locked to the pipe 17 so as to prevent detachment of the pipe 17; and a first caulked part 39 to be locked to the swollen part 24.