An aspect of the present disclosure may include a gas lock cover secured to a nozzle holder and provided downstream of a nozzle. The gas lock cover may cover a periphery of an exit of the nozzle and be structured to guide gas supplied from a gas supply unit. The gas lock cover may include a hollow cylindrical part provided downstream of the nozzle and having an exit opening for outputting droplets that are outputted from the nozzle and pass through an internal cavity of the cylindrical part. The gas lock cover may include a channel for transmitting the gas supplied from the gas supply unit, the channel being structured to orient a flow of the transmitted gas so as to flow to the exit opening of the cylindrical part through the internal cavity of the cylindrical part.