Cooling device of numerical control machine tool

A cooling device of a numerical control machine tool comprises a tool bar connected with a spindle and a tool bit connected with the tool bar. A cooling mechanism is arranged on the numerical control machine tool and comprises a high-pressure oil tank. A first oil delivery pipe communicated with the high-pressure oil tank is arranged in the spindle, a second oil delivery pipe communicated with the first oil delivery pipe is arranged in the tool bar, a third oil delivery pipe communicated with the second oil delivery pipe is arranged in the tool bit, and an outlet of the third oil delivery pipe is formed in the end face of the tool bit. An oil cavity is formed in the spindle, and the first oil delivery pipe is communicated with the second oil delivery pipe through the oil cavity. A one-way valve is arranged at the position, at an outlet of the oil cavity, of the first oil delivery pipe. Two fourth oil delivery pipes are arranged in the tool bar, one end of each fourth oil delivery pipe is communicated with the oil cavity, and an opening in the other end of each fourth oil delivery pipe is formed in the lower middle portion of the outer side face of the tool bar. The cooling device has the advantages of being simple and reasonable in structure, flexible to operate and long in service life.