According to one embodiment, water storage tank has a space in an interior of the water storage tank. Water is stored in the space. The tank includes a lower enclosure, an upper enclosure, and a bonding member. The upper enclosure is positioned on the lower enclosure. The space is formed by the upper enclosure being bonded to the lower enclosure. The upper enclosure is longer than the lower enclosure in a vertical direction. The bonding member bonds the lower enclosure and the upper enclosure and is positioned between the lower enclosure and the upper enclosure. The lower enclosure has a concave part provided on the space side of the bonding member. The upper enclosure has a convex part provided on the space side of the bonding member. The convex part is engaged with the concave part.