PURPOSE: To smoothly connect a corrosionproof steel pipe in a proper condition so as to surely prevent a pipe end of the steel pipe from corrosion by providing an engaging part, which impedes rotation or displacement of a core, in an internal surface of a joint main unit in which the core is formed.

CONSTITUTION: In a pipe joint 1, protrusive engaging parts 2c, 2c are formed in a joint main unit internal surface recessed part 2b where an outer tubular part 3a of a core 3 is positioned. Since the protrusive engaging parts 2c, 2c are respectively formed in two mutually opposed parts of the joint main unit internal recessed part 2b and engaged with the core outer tubular part 3a, in the pipe joint 1, these engaging parts serve as resistance relating to rotation and displacement of the core 3. Accordingly, the core 3, even when turning force is applied to act, is prevented from being rotated and displaced, to hold the initial predetermined position. In this way, in the case that a corrosionproof steel pipe is screwed into the pipe joint 1, a trouble, such that the core 3 in a joint main unit 2 is rotated and displaced by friction force of screwing the pipe, is surely prevented.