A medical joint, comprising: a connection tube including a first tube and a second tube extending from and communicating with the first tube, two ends of the first tube including a communicating opening and a first junction respectively, a distal end of the second tube including a second junction; and a check valve module assembled to the communicating opening to seal the same, the check valve module including a first membrane and a second membrane disposed overlappingly, the first membrane including a first slit, the second membrane including a second slit; wherein the first slit and the second slit intersect each other, characterized in that the first tube forms a rim at the communicating opening, the first membrane includes a first plate and an annular wall extending from a periphery of the first plate, the annular wall forms a stop ring extending outwardly from one end of the annular wall disposed away from the first plate, the first slit is formed on the first plate, the annular wall is inserted in the first tube and contacts the same, the stop ring and the rim abut each other for securement therebetween, the first tube includes two vents opposite to each other, the annular wall includes two through holes opposite to each other, the second membrane includes a second plate and two wings extending from two sides of the second plate, a protrusion extends from a distal end of each of the wings, the second slit is formed on the second plate, the second plate and the first plate overlap and contact each other, the wings pass through the respective through holes and the respective vents for securement, and the protrusion and the first tube engage each other. a connection tube including a first tube and a second tube extending from and communicating with the first tube, two ends of the first tube including a communicating opening and a first junction respectively, a distal end of the second tube including a second junction; and a check valve module assembled to the communicating opening to seal the same, the check valve module including a first membrane and a second membrane disposed overlappingly, the first membrane including a first slit, the second membrane including a second slit; wherein the first slit and the second slit intersect each other, characterized in that the first tube forms a rim at the communicating opening, the first membrane includes a first plate and an annular wall extending from a periphery of the first plate, the annular wall forms a stop ring extending outwardly from one end of the annular wall disposed away from the first plate, the first slit is formed on the first plate, the annular wall is inserted in the first tube and contacts the same, the stop ring and the rim abut each other for securement therebetween, the first tube includes two vents opposite to each other, the annular wall includes two through holes opposite to each other, the second membrane includes a second plate and two wings extending from two sides of the second plate, a protrusion extends from a distal end of each of the wings, the second slit is formed on the second plate, the second plate and the first plate overlap and contact each other, the wings pass through the respective through holes and the respective vents for securement, and the protrusion and the first tube engage each other.