To cope with assembly of a product with large assembly load by constituting an assembly production line in a loop so as to allow a plurality of components to be picked into an empty assembly pallet returning to the most upstream part of the line, and by omitting a return conveyer only for returning the assembly pallet.

The assembly production line is structured in a loop conveying numerous pallets. The line includes a base component: setting station for setting base components of the product on the pallet; an assembly zone for assembling the plurality of components with the base component on the pallet; a take-out station for taking out the product from the pallet; and a plurality of component shelves provided between the take-out station and the base component setting station for storing the plurality of components by type for setting the component on a setting part of each empty pallet by component instruction information.