The invention provides a device and a process for the surface treatment of parts. The device comprises a transportation unit and a treatment unit, wherein the transportation unit is arranged on the upper side of the treatment unit and used for transporting a preliminarily-machined part into the treatment unit; the treatment unit comprises a cleaning pool, an air furnace, a nitriding furnace, an oxidizing furnace, a cooling chamber, an ultrasonic cleaning device, a polishing machine and an oxidation repairing furnace which are arranged in sequence; a first gas transportation pipeline communicates with a nitriding cavity and used for transporting nitrogen gas into the nitriding cavity; and a second gas transportation pipeline communicates with a cooling cavity and used for transporting protective gas into the cooling cavity. By adoption of the device and the process, the nitrogen gas is injected when the surface of the part is subjected to nitriding treatment in the nitriding furnace, thereby facilitating the flow of a nitriding salt solution in the nitriding furnace, improving the nitriding speed, and reducing the deformation; and the part is cooled in the cooling chamber which is fully filled with the protective gas, so that the surface color of the part is uniform and the deformation is little.