To flexibly adapt to changes in production plans or machining conditions and malfunctions in a conveyor.

A control panel 6 obtains machining states of respective machining machines 11-118 and operation states of respective carriers 31-36 and performs sequence control of workpiece conveyance by the respective carriers, movement/retreat thereof, workpiece transfer, and conflict avoidance between the carriers. A computer 7 sequentially selects one of the carriers in accordance with machining and operation states and informs the control panel of workpiece conveyance, movement/retreat and workpiece transfer by the selected carrier. A remaining machining time is obtained in accordance with a combination pattern of a machining device for a workpiece to be carried, machining time data thereof and the machining and operation states, and a carrier which is transferable to subsequent machining device is selected in the order of the workpieces of which remaining machining time is short in accordance with data of effective movable range of each carrier which is classified by pattern.