A washing machine includes a cabinet, a tub provided inside the cabinet to store wash water therein, a drum rotatably provided inside the tub, and a balancer comprising an upper side surface covering an outer surface of a bottom of the drum and a lower side surface formed at one side of the upper side surface in a planar shape while facing an inner surface of a bottom of the tub. The balancer is configured to counterbalance an unbalanced load of the drum, thereby saving energy and enhancing balancing efficiency.