Abstract: A tube coupling according to the present invention comprises a coupling body, a separation prevention ring which is disposed in the coupling body to bite into the outer wall of a tube body fitted into the coupling body so to prevent the tube body from coming out, and a release ring which is disposed in the coupling body so to be movable in an axial direction within a predetermined range and releases the separation prevention ring from the tube body by pushing the separation prevention ring, wherein the separation prevention ring comprises a ring portion which contacts a back ring disposed in the coupling body; pushing portions which are radially formed in a large number within the ring portion, has a circular shape, have grooves which extends from the outside of the ring portion to the inside, and are pushed by an inside end of the release ring; and projections which are respectively formed at the tips of the pushing portions and pulled out of the outer wall of the tube body when they are pushed by the inside