Manifold unit and constant flow rate-type leak tester using same

In this manifold unit, a workpiece-side pipe, a master-side pipe, an introduction hole, and an open hole are formed within a manifold block. Two pipe openings that are electrically connected to each of the workpiece-side pipe and the master-side pipe and a shared opening that is electrically connected to the introduction hole are formed in a first circular area of the surface of the manifold block. Critical flow nozzles are inserted into each of the two pipe openings in the first circular area. Two pipe openings that are electrically connected to each of the workpiece-side pipe and the master-side pipe and a shared opening that is electrically connected to the open hole are formed in a second circular area. First and second mount plates are arranged so as to cover the first and second circular areas. The first and second mount plates each comprise: cylindrical protrusions in which through holes that face and connect with the pipe openings are formed; and through holes that face and connect with the shared openings. Control valves that are mounted on the mount plates use a rubber seal to simultaneously open and close the through holes of the two cylindrical protrusions in a valve operation chamber.