The invention relates to a tube bending machine. The tube bending machine comprises a rack, wherein a loading mechanism capable of outputting front-and-back linear displacement actions is arranged on the rack, a prop-bending die is in transmission connection with a power output end of the loading mechanism, two support wheels matched with the prop-bending die to bend corresponding metal tubes are also rotationally arranged on the rack, metal tube limiting mechanisms are arranged in positions, which are located on left and right sides of each support wheel, of the rack, each metal tube limiting mechanism is provided with a limiting channel which extends linearly and laterally and is penetrated through by the corresponding end of each metal tube, and the limiting channels are located on back sides of the corresponding support wheels respectively and provided with channel walls which are in stop fit with the corresponding ends of the metal tubes in the front-and-back direction and in sliding friction guide fit with the corresponding ends of the metal tubes bilaterally when the prop-bending die and the support wheels prop and press the metal tubes. The tube bending machine is not required to be manually held by an operator during usage and can bend R angles.