A tank includes a container part having an upper wall, a sidewall and a bottom wall to store a processing liquid therein, a liquid discharge passage installed at a position higher than a liquid surface of the processing liquid stored in the container part to discharge the processing liquid into the container part, and a gas discharge passage installed at a position higher than the liquid surface to discharge a gas into the container part. The liquid discharge passage discharges the processing liquid from the liquid discharge port so that the processing liquid is brought into contact with a portion above the liquid surface of an inner surface of the sidewall. The gas discharge passage discharges the gas from the gas discharge port so that the gas is brought into contact with a portion above the liquid surface of an inner surface of the container part.