An additive manufacturing apparatus of the disclosure includes: a supply port that supplies an inert gas to a chamber; a supply nozzle which is attached to the supply port and releases two layers of airflow having different speeds toward the window; and a discharge port that discharges the inert gas from the chamber. The supply nozzle has: a first nozzle member having an inlet surface connected to the supply port; a net-like member which has a plurality of through holes and is attached in a manner of covering a portion of a lower part of an outlet surface of the first nozzle member; and a second nozzle member that is attached to the upper side of the outlet surface of the first nozzle member.