A projection apparatus that projects an image or a video onto a screen disposed in an indoor space , the projection apparatus comprising: a plurality of two-fluid nozzles each of which mixes a liquid with a gas, and sprays a mist in which the liquid is atomized; a projection-apparatus-side-gas-flow-path through which the gas is supplied to the plurality of two-fluid nozzles ; a gas valve that opens and closes the projection-apparatus-side-gas-flow-path ; a gas supply source that supplies the gas to the projection-apparatus-side-gas-flow-path ; a projection-apparatus-side-liquid-flow-path through which the liquid is supplied to the plurality of two-fluid nozzles ; a liquid valve that opens and closes the projection-apparatus-side-liquid-flow-path ; a liquid supply source that supplies the liquid to the projection-apparatus-side-liquid-flow-path ; a liquid pressure adjuster that is provided at the projection-apparatus-side-liquid-flow-path between the plurality of two-fluid nozzles and the liquid valve ; a projector that projects the image or the video onto the screen whereby light of the image or the video is scattered in the mist ; a mist concentration measurer that measures a mist concentration in the indoor space in which the mist is sprayed; and a controller that starts and stops spraying of the mist by controlling the gas valve and the liquid valve on the basis of the image or the video projected onto the screen from the projector , receives a signal indicating the mist concentration from the mist concentration measurer , and starts and stops spraying of the mist by controlling the gas valve and the liquid valve on the basis of the received signal, and thus controls the mist concentration. a plurality of two-fluid nozzles each of which mixes a liquid with a gas, and sprays a mist in which the liquid is atomized; a projection-apparatus-side-gas-flow-path through which the gas is supplied to the plurality of two-fluid nozzles ; a gas valve that opens and closes the projection-apparatus-side-gas-flow-path ; a gas supply source that supplies the gas to the projection-apparatus-side-gas-flow-path ; a projection-apparatus-side-liquid-flow-path through which the liquid is supplied to the plurality of two-fluid nozzles ; a liquid valve that opens and closes the projection-apparatus-side-liquid-flow-path ; a liquid supply source that supplies the liquid to the projection-apparatus-side-liquid-flow-path ; a liquid pressure adjuster that is provided at the projection-apparatus-side-liquid-flow-path between the plurality of two-fluid nozzles and the liquid valve ; a projector that projects the image or the video onto the screen whereby light of the image or the video is scattered in the mist ; a mist concentration measurer that measures a mist concentration in the indoor space in which the mist is sprayed; and a controller that starts and stops spraying of the mist by controlling the gas valve and the liquid valve on the basis of the image or the video projected onto the screen from the projector , receives a signal indicating the mist concentration from the mist concentration measurer , and starts and stops spraying of the mist by controlling the gas valve and the liquid valve on the basis of the received signal, and thus controls the mist concentration. <EOS>