Spacecraft and antenna apparatus that can be more easily deployed from a stored state can include: a main-reflection unit including a plurality of ribs formed to be deployable in a stored state in which the ribs are folded and a sheet body provided between a plurality of the ribs and configured to be capable of reflecting a radio wave radiated from a radiator and emitting the radio wave outside, and a restriction member configured to restrict deployment of the plurality of ribs in the stored state, and release the restriction by operation of a restriction release member different from the main-reflection unit.