Provided is joint unit having a resin tube, a joint structure, and a nut, the joint structure has a guide part that guides the outer circumferential face of the resin tube, a protrusion that forms an insertion groove between the guide part and the protrusion, and a fixing part that fixes the resin tube inserted in the insertion groove, the tip of the protrusion is located closer to a main body than the tip of the guide part, the nut has a recessed part having an inner diameter greater than a first outer diameter of the guide part and smaller than a second outer diameter of the fixing part, and the tip of the fixing part in contact with the recessed part bites into the outer circumferential face of the resin tube in a state where the nut is fastened to the joint structure.