Liquid to be injected from an injection nozzle is supplied through a liquid supply channel toward the injection nozzle. Negative pressure for sucking the liquid injected from the injection nozzle through a suction port is produced by a suction unit and guided through a suction channel toward the suction port. A bypass channel which bypasses the liquid supply channel on the upstream side with respect to the injection nozzle and connects with the suction channel is provided. The bypass channel is opened and closed by an opening and closing unit. According to this structure, flow of unnecessary liquid from the injection nozzle can be reduced by opening the opening and closing unit while injection of liquid is stopping.