To provide a processing line of parts using an unmanned conveying vehicle, which reduces variation of accuracy for positioning the parts to a working machine.

A rough guide part loading and guiding parts 20 to a positioning condition having a tolerance relative to a precise position at the time of processing parts is provided to an unmanned conveying vehicle 10. At least a first working area A1 for loading the parts to the rough guide part of the unmanned vehicle 10, a second working area A2 for precisely positioning the parts at the time of processing by a part positioning mechanism 30 for directly gripping and precisely positioning the parts 20 and providing a working machine for processing the parts by processing means 49, and a third area A3 for picking up the processed parts 20 from the rough guide part of the unmanned conveying vehicle 10 are set in the processing line. A positioning condition having a tolerance by the rough guide part is within a range capable of gripping the parts 20 when precisely positioned by the part positioning mechanism 30 of the working machine.