An embodiment of this invention provides a swivel joint for a working machine that makes it easy to install a device for detecting rotation angle and is able to suppress the increase of the size due to the installation of the device. An embodiment of the present invention includes the swivel joint that includes an outer body being secured on one of the lower traveling body and the upper swiveling body and having a blocking surface on one end; an inner body being secured on another of the lower traveling body and the upper swiveling body and being relatively and rotatably fitted in the outer body while opposing to the blocking surface at one end n in the manner of making a space; a pilot oil passage being formed on rotational center line CL of the inner body for distributing pilot oil; a rod being inserted into the pilot oil passage and being secured on one of the outer body and the inner body; and a rotation angle sensor being secured on the other end of the outer body and the inner body for detecting a rotation angle of the rod.