A moving element (21) holding a workpiece (a hub unit bearing (1)) is horizontally loaded into an internal space (23) of an exterior (17) from an external space of the outer package (17), while being guided by a guide member (20) through an opening portion (a front surface side opening portion (25)) provided in the exterior (17) constituting a rotary forging apparatus (16). After completion of the loading process, the workpiece is subjected to rotary forging, using a forming die (18).