Abstract: A synthetic resin valve in which a body is connected end-to-end in abutting relationship to a cylindrical body cap having a flange at one end and a seat at the other end by screwing the two together with a cap nut. The seat includes a ring-like element having a lesser diameter portion which is fitted into an annular groove adjacent to a front end portion of the body cap, and a greater diameter portion which engages the outer peripheral surface of the front end portion of the body cap, the front face of the larger diameter portion of the ring-like element preferably resting in the same plane as the front face of the body cap which abuts the body. The ring-like element is cut radially in one circumferential region so that it may be deformed around the body cap such that its smaller diameter region may be fitted into the annular groove, and has a rear wall for engaging the cap nut.