As a production line for producing target products, a production line that conveys a plurality of pallets for setting workpieces (intermediates of the target products) along a loop-shaped circulation route and sequentially performs a plurality of production processes (assembly, processing, etc. of components) on the workpiece that is set on each pallet is known (e.g., see Patent Documents 1 and 2).
Each pallet has a holding shape (a bracket or the like) for setting (holding) the workpiece, but it is not usually manufactured with high precision. For this reason, positioning precision of the workpiece by the holding shape is not high, and a setting position of the workpiece on the pallet is slightly different for each pallet. Therefore, in the aforementioned production line of the related art, with regard to the production process required to be performed after an accurate setting position of the workpiece on the pallet is identified among the production processes, when the production process is performed, the accurate setting position of the workpiece on the pallet is measured using an expensive camera (an image processor) or a sensor
However, in this production line of the related art, there is a problem that, depending on the number of production processes that are performed after the accurate setting position of the workpiece on the pallet is identified, the number of expensive cameras or sensors for measuring the accurate setting position of the workpiece on the pallet is increased.