A conduit forming unit includes: a cylindrical tubular body having flanges, on both end portions of the cylindrical tubular body; a first connection tubular body and a second connection tubular body respectively connected to a first end portion and a second end portion of the cylindrical tubular body; and tube joints for connecting the cylindrical tubular body and the first connection tubular body and the second connection tubular body to each other. The tube joint includes: a pawl equipped nut where a plurality of pawl portions which are engageable with the flange of the cylindrical tubular body are formed in the pawl equipped nut, the pawl portions engage with the flange so as to connect the first connection tubular body and the cylindrical tubular body to each other; and a retaining ring being annularly mountable on the pawl equipped nut and retaining engagement of the pawl portions with the flange.