A processing apparatus includes: a plurality of process modules concatenated with one another; and a loader module configured to receive a carrier accommodating a plurality of substrates to be processed by the plurality of process modules, wherein each of the plurality of process modules includes: a heat treatment unit including a processing container configured to accommodate the plurality of substrates and perform a heat treatment on the plurality of substrates; and a gas supply unit disposed on one side surface of the heat treatment unit and configured to supply a gas into the processing container.