To provide a pipe mounting structure for a power cylinder, which arbitrarily selects a direction for connecting the pipe by a simple structure.

An elbow joint 30 for connected the pipe 17 to a cylinder tube 9a of the power cylinder 9 includes: a first portion 37 thread-fixed to a connection hole 32 penetrated through with the cylinder tube 9a along a predetermined axis 31; and a second portion 37 extending in a direction X1 crossing to the first portion 36 and connecting the pipe 17 along the direction X1. At least one of a screw part 35 of an inner periphery of the connection hole 32 and a screw part 44 of an outer periphery of the first portion 36 of the elbow joint 30, is made to an unequal pitch. The second portion 37 is fixed toward an arbitrary direction around a predetermined axis 31.