A structure of a resin-made pipe joint in which, when the pipe joint is coupled to a tube, the tube hardly slips off, and the sealing property with respect to the tube can be stably ensured is provided. In a structure of a resin-made pipe joint having a sleeve 4, a joint body, and a union nut, the sleeve has a first outer circumferential surface 41, a second outer circumferential surface 52, and an annular step portion 53. The first outer circumferential surface 41 is disposed in a tapered manner so as to be further flared as advancing from one axial side toward the other side in order to flare one longitudinal end portion of the tube. The second outer circumferential surface has an outer diameter which is smaller than the maximum outer diameter of the first outer circumferential surface, and is disposed on the other axial side of the first outer circumferential surface. The step portion is a step portion which is disposed between the first outer circumferential surface and the second outer circumferential surface, and has an edge portion 54 on the side of the first outer circumferential surface. The edge portion is contacted with a part of the inner circumferential surface of the tube when the sleeve is press-inserted into the one longitudinal end portion of the tube.