The invention discloses an automatic rod adding machine of a rod mill. The machine comprises a rack body portion for storing steel rods, an arm rack portion moving forward and backward on the guide rail of the rack body portion and throwing the steel rods into the rod mill, a rod poking device for poking the steel rods from the rack body portion to the arm rack portion, a running system for making the rack body portion to run, and a spacing control system for controlling the running displacement of the rack body portion and the running displacement of the arm rack portion. The rod adding machine has a simple structure, is convenient to dismount and mount, can vertically and transversely move through the running system, and is suitable for various diameters and lengths of steel rods, and also has the advantages of realization of matching of one machine with various specifications of the rod mill, strong versatility and investment cost reduction.