To provide a clamping device capable of clamping a flexible tube in a good manner without fail and also capable of intercepting the flow of a fluid in the flexible tube more exactly. A clamping device 1 includes a one end portion 2 having a locked part 5 at a tip, an other end portion 3 having a locking part 6 capable of locking the locked part 5, and insertion holes H1 and H2 allowing a flexible tube T to be inserted between a first projection 2a and a second projection 3a. In a clamped state, the first projection 2a and the second projection 3a are positioned close to each other, and the flexible tube T is thus clamped. Consequently, the flow of a fluid is intercepted at the clamped position. The other end portion 3 has interfering parts 7. When the one end portion 2 is further pressed with the locked part 5 being locked by the locking part 6, the interfering parts 7 interfere with predetermined points P1 and prevents further movement of the locked part 5.
