<p>A storage tank (41) is partitioned with a partitioning member (25) into a humidification zone (31) and a supply zone (32), and the upper part of the supply zone (32) is covered with a covering member (26). The partitioning member (25) has a communication path (33) which is immersed in water and can allow the supply zone (32) and the humidification zone (31) to communicate with each other. An active species generated in a discharge treatment unit (51) is supplied to the supply zone (32), in which the purification of water is carried out. The active species supplied is prevented from being released to the outside by the partitioning member (25) and the covering member (26). The water in the supply zone (32) which is purified with the active species flows into the humidification zone (31) through the communication path (33).</p>
