PURPOSE: To make it possible to use an extended life reverse radius seal ring by providing a long tubular housing, a long tubular nipple, and an annular seal ring disposed between the sealing surfaces of the housing and the collar of the nipple.

CONSTITUTION: The rotary joint has a long tubular housing, a chamber formed within the housing, and a sealing surface 44 forming a part of the chamber. A long tubular nipple 28 is provided within the housing concentrically, which is movable along the axial direction and rotatable. An annular seal ring 46 is provided between a wear plate 16 and a collar 36 of the nipple 28, i.e., between the sealing surface 44 of the housing and the sealing surface 52 of the collar 36. Slots 60 assist lubrication between the sealing surface 52 and the outer plane of the seal ring 46. Thus, a rotary joint using an extended life reverse radius seal ring is obtained.