The invention discloses a process device with the combination of rough machining and fine machining of centreless grinding and lapping and polishing of an abrasive belt. The device comprises a piece riding wheel, a guide wheel, an abrasion head, a transition gear, a fixing gear, a two-shaft motor, a centreless abrasive head of the abrasive belt, and a supporting member of the piece riding wheel, wherein the centreless abrasive head of abrasive belts is composed of an abrasion head driving gear, the abrasive belt and an abrasive head contacting gear, and the abrasion head driving gear is connected with the abrasive head contacting gear via the abrasive belt. One end of the two-shaft motor is in fixed connection with the abrasive head driving gear, and the other end is connected with a fixed gear which is matched with the transition gear. The transition gear is matched and connected to the abrasive head. The device resolves the problems of poor rigidity, a lot of process procedures, a plurality of devices, much transport, complex operation, inconvenient installation and the like in the prior art of the coarse grinding, fine grinding, polishing and the like of the outer circle with elongated circular rods. The device increases the integral efficiency, reduces manufacture cost, enlarges the manufacture range and combines the rough process, semi-fine process, fine process, lapping and polishing.