To tightly hold resinous tubes against their falling-off with a tube coupling with improved sealing performance, which is constituted of a smaller number of component parts for its lower manufacturing costs.

A tube coupling body A involves a pipe part on the side of tube coupling, which comprises a swelling portion 10a on the outer periphery at its opening for receiving an expanded resinous tube C force-fitted thereon, a consecutive pipelike portion 10b having outside diameters smaller than the maximum outside diameter of the swelling part 10a and larger than the inside diameter of the tube C for holding the tube C expanded, and a consecutive externally threaded portion 10c. With the tube C being fitted over the swelling portion 10a and the pipelike portion 10b, a pressure ring B loosely fitted on the tube C in advance is brought into mesh at its internally threaded portion 12 with the externally threaded portion 10c until its tube insertion port butts against the swelling portion 10a to thereby press a portion 11a of the tube C forward and thus produce a seal portion 13 in the tube C. The tube C is thus sealed under its close contact with the swelling portion 10a and the pipelike portion 10b at two positions.