A clamping device comprises a driving cylinder, a buffering assembly, a first clamping member, and a second clamping member. The first clamping member and the second clamping member are mounted to the driving cylinder. The buffering assembly comprises a fixing member, a guiding rail, a guiding rod, and an elastic member. The fixing member comprises a first mounting portion and a second mounting portion. The first mounting portion defines a through hole. The guiding rail is mounted to the fixing member and located between the first mounting portion and the second mounting portion. The driving cylinder is mounted to the guiding rail. A first end of the guiding rod is movably received through the through hole, and a second end of the guiding rod is fixed to the driving cylinder. Opposite ends of the elastic member resist against the first mounting portion and the driving cylinder, respectively.