A manufacturing method and an apparatus enable high productivity. A method for manufacturing an oxidized fiber bundle includes joining an upstream precursor fiber bundle and a downstream precursor fiber bundle together with a joining fiber bundle, and oxidizing the joined precursor fiber bundles by feeding the joined precursor fiber bundles through an oxidization furnace. The joining includes applying an oiling agent to a joint area of a joining target precursor fiber bundle before joining the joining target precursor fiber bundle and the joining fiber bundle together. A quantity of the oiling agent adhering to the joint area is 0.15 to 0.85 wt %.