A washing tub array may be configured to guide water flow in a washing tub upward. The washing tub may comprise an outer tub, an inner tub, and a tub cover. The tub cover may include a side surface formed to extend in a longitudinal direction along a circumference of the outer tub, the side surface being coupled to the top of the outer tub, a curved surface extending from a top of the side surface to have a curvature and formed to decrease in diameter upward, wherein a water flow guide hole is formed through both sides of the curved surface, and a planar surface formed to extend in a transverse direction from the curved surface so as to cover the circumference of the upper surface of the inner tub.