The utility model belongs to the technical field of engineering machinery and discloses a full-automatic steel bar shearing machine. According to the full-automatic steel bar shearing machine, a steel bar shearing knife is connected with a machine frame through a sliding rail structure, an automatic overturning plate is arranged on one side of the machine frame, a normally-open contact which can be touched by the end of a steel bar is arranged on the other side of the automatic overturning plate and is connected with an electromagnetic control device, when a steel bar to be sheared touches the normally-open contact, the normally-open contact is closed, the electromagnetic control device is started, the steel bar is cut off through the steel bar shearing knife, the sheared steel bar is conveyed to a specific position through the automatic overturning plate, and in this way, the labor intensity is greatly relieved, and the labor efficiency is improved. According to the full-automatic steel bar shearing machine, due to the fact that the sliding rail structure and a reset spring are arranged between the steel bar shearing knife and the machine frame, the steel bar shearing knife can slide on a sliding rail in a reciprocating mode. When the steel bar shearing knife shears the steel bar, the steel bar shearing knife and the steel bar can move synchronously on the sliding rail, the steel bar shearing knife return to the original position under the action of the reset spring after the steel bar is sheared, and the rate of breakage of the steel bar shearing knife is greatly decreased.