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 includes a one end portion having a locked part at a tip, an other end portion having a locking part capable of locking the locked part, and insertion holes allowing a flexible tube to be inserted between a first projection and a second projection. In a clamped state, the first projection and the second projection are positioned close to each other, and the flexible tube is thus clamped so that the flow of a fluid is intercepted at the clamped position. The other end portion has interfering parts. When the one end portion is further pressed with the locked part being locked by the locking part, the interfering parts interfere with predetermined points and prevents further movement of the locked part.
