A tool changing device comprises a tool magazine, a clamping assembly and a rotating telescopic air cylinder, wherein tools are installed in the tool magazine. The rotating telescopic air cylinder is installed close to the tool magazine and used for clamping the tools on the tool magazine. The clamping assembly comprises a tool changing arm and two clamping components respectively installed at two ends of the tool changing arm, and the rotating telescopic air cylinder is connected with the tool changing arm and can drive the tool changing arm to rotate, stretch out and draw back. Each clamping component comprises an installation piece, an elastic piece, a piston and a plurality of abutting pieces. For each clamping component, the installation piece is installed on the tool changing arm, a plurality assembly holes are formed in the circumferential wall of the installation piece in a penetrating mode, the elastic piece and the piston are sleeved on the installation piece, two ends of the elastic piece are respectively and elastically abutted against the installation piece and the piston, and the plurality of abutting pieces are respectively and movably installed in the plurality of assembly holes in the installation piece and abutted against the piston. The tool changing device has the advantage of being high in clamping accuracy.