PURPOSE: To provide a method for preferentially distributing workpieces, in a line in which devices of the same working function are arranged in series to each other to supply the workpieces thereto followed by working, to the upper stream and lower steam of a carrying means and operating machines with light load and heavy load, respectively, to effectively operate the lime.

CONSTITUTION: An operation request signal (a) and a load level signal (b) are transmitted from operating machines 6, 7, 8, 9, 10 arranged on a carrying means 5 to a request receiver 2 and a load judging device 3 in an operation controller 1, respectively, and compared with the load state of the operating machines downstream from the operation-requesting operating machine by the load judging device 3. When the present load of the operating machine under request is smaller than the downstream operating machine loads, for example, operation OK is judged, and an operation command signal (c) is transmitted from an operation command device 4 to the operating machine to distribute workpieces first to the downstream working machine with a low load.