Abstract: The present invention relates to a tube coupling for connecting tubes for conveying a fluid. The present invention provides a tube coupling that may confine separation of a collet. The present invention also provides a tube coupling that may prevent plastic deformation of a collet to so that a reliability of the tube coupling is improved and a life span of the tube coupling is guaranteed. The present invention also provides a tube coupling that may interrupt a direct contact between a collet and an O-ring seal so that leakage of a fluid is prevented from occurring due to damage of an O-ring seal and a tube is guided to a center of the O-ring seal and is inserted in the O-ring seal.