A manufacturing method of a frame structure for an image forming apparatus, the frame structure including
- a first stay including a first and a second welding surface welded to a frame assembly,
- a second stay including a third and a fourth welding surface welded to said frame assembly,
- a third stay including a fifth and a sixth welding surface welded to said frame assembly,
- at least one supporting portion provided on each of said first stay, said second stay and said third stay and configured to support said frame assembly on an installation surface in contact with said installation surface,
- a first opposing surface of said frame assembly opposing said first welding surface and welded with said first welding surface,
- a second opposing surface of said frame assembly opposing said second welding surface and welded with said second welding surface,
- a third opposing surface of said frame assembly opposing said third welding surface and welded with said third welding surface,
- a fourth opposing surface of said frame assembly opposing said fourth welding surface and welded with said fourth opposing surface,
- a fifth opposing surface of said frame assembly opposing said fifth welding surface and welded with said fifth welding surface, and
- a sixth opposing surface of said frame assembly opposing said sixth welding surface and welded with said sixth opposing surface,
- said frame assembly being welded with said first stay, said second stay and said third stay so that said frame assembly supported to said installation surface by a plurality of said supporting portions is not contact with said installation surface, said manufacturing method comprising:
- a fixing step of fixing said frame assembly to a jig in a state in which said frame assembly is not contact with said installation surface;
- a adjusting step of adjusting a position of said first stay to said frame assembly by moving said first stay in a vertical direction in a state in which said first welding surface contacts said first opposing surface and said second welding surface contacts said second opposing surface, adjusting a position of said second stay to said frame assembly by moving said second stay in the vertical direction in a state in which said third welding surface contacts said third opposing surface and said fourth welding surface contacts said fourth opposing surface, and adjusting a position of said third stay to said frame assembly by moving said third stay in the vertical direction in a state in which said fifth welding surface contacts said fifth opposing surface and said sixth welding surface contacts said sixth opposing surface;
- and
- a welding step of welding said first welding surface to said first opposing surface, welding said second welding surface to said second opposing surface, welding said third welding surface to said third opposing surface, welding said fourth welding surface to said fourth opposing surface, welding said fifth welding surface to said fifth opposing surface, and welding said sixth welding surface to said sixth opposing surface in a state in which said plurality of said supporting portions contact said installation surface and said frame assembly is not contact with said installation surface.