Abstract: A clamping device includes a first handle, a second handle, and a positioning unit. The positioning unit includes a sleeve pivotally mounted on the first handle, a rack pivotally mounted on the second handle and movably mounted in the sleeve, a control member pivotally mounted on the sleeve and having a first end extended into the sleeve, and a locking member mounted on the first end of the control member to move therewith and detachably engaged with the rack to limit movement of the rack. Thus, the locking member on the sleeve is normally engaged with the rack, so that the first handle and the second handle are positioned by the positioning unit rigidly and stably, thereby facilitating a user operating the claimping device.