To provide a swivel joint having a simple structure for preventing loosening of a rotor and being easy to assemble.

In a swivel joint, a projecting part 4a which projects in the form of a semicircle is formed at a semicircular part formed inside a cover 4, and a small diameter part 3c inserted in an oil chamber 6 is formed at the end of a rotor 3 inserted in a housing 1, with an annular groove 3d formed in the small diameter part 3c. Since the projecting part 4a is engaged in the annular groove 3 over almost half of its range, the rotor 3 is always prevented from coming out of the housing 1.