To provide a production device which can accomplish reduction in installation space for production equipment as a whole and in a cost for the equipment and is suitable for production of an automobile door for which multi- item small quantity production is desired.

In respective stations S1-S7 of a production assembly line in which a plurality kinds of workpieces 1 for an automobile are mixed, workpiece conveyance and workpiece retention are carried out by means of a pair of belt conveyors B1-B7 which can easily comply with multi-item workpieces. In the sealer applying station S2 and the welding station S6 for workpiece production machining, an upper face and a lower face of a rotary type surface plate are used selectively in compliance with the multiple kinds of workpieces. In the hemming station S4, a plurality kinds of press dies are stacked vertically so as to be moved laterally, so that compliance with the plurality kinds of workpieces can be accomplished. In this way, reduction of a space and a cost of the automobile door production equipment as a whole can be facilitated.