A laundry treating apparatus comprising: a cabinet including a laundry introduction hole formed therein to introduce laundry; a drum rotatably provided in the cabinet, the drum comprising a drum introduction hole, formed in a front surface thereof, in communication with the laundry introduction hole; at least three main balancers provided in the drum defining a space where liquid is stored, the main balancers being spaced apart in a circumferential surface of the drum at preset angle intervals with respect to a rotation axis of the drum and each main balancers including: a storage body fixed to an inner circumferential surface of the drum to define a space where the liquid is stored; an inlet (553a, 553b) through which the liquid is drawn into the storage body; and an outlet through which the liquid stored in the storage body is exhausted outside the drum; balancer inlet holes (313, 315, 317) provided in the front surface of the drum to communicate with the inlet (553a, 553b) provided in each of the main balancers; and a passage unit (51, 52, 57) provided in the front surface of the drum and configured to guide liquid to the balancer inlet holes (313, 315, 317), characterized by: a sub balancer provided at the front surface of the drum to provide a circulation passage of liquid, the sub balancer increasing the load of the drum locally by being configured to guide the liquid stored in the circulation passage toward the lowest point of a drum rotation locus when laundry causing unbalance moves toward the highest point of the drum rotation locus; a supplier configured to selectively supply liquid to the main balancer and the sub balancer, the supplier including a passage unit supplying unit (592, 592a, 594, 594a, 596, 596a) to supply liquid to the passage unit and a sub balancer supplying unit (597, 596) to supply liquid to the sub balancer; a control unit configured to determine that the laundry causing the unbalance passes the lowest point of the drum rotation locus based on a signal of a sensing unit and to control the liquid to be supplied via the supplier to a specific one of a first passage and a second passage of the passage unit and to the sub balancer for a preset time period to damp the unbalance, wherein the sub balancer is configured to exhaust the liquid stored in the circulation passage outside the circulation passage when the rotation speed of the drum decreases. a storage body fixed to an inner circumferential surface of the drum to define a space where the liquid is stored; an inlet (553a, 553b) through which the liquid is drawn into the storage body; and an outlet through which the liquid stored in the storage body is exhausted outside the drum; a sub balancer provided at the front surface of the drum to provide a circulation passage of liquid, the sub balancer increasing the load of the drum locally by being configured to guide the liquid stored in the circulation passage toward the lowest point of a drum rotation locus when laundry causing unbalance moves toward the highest point of the drum rotation locus; a supplier configured to selectively supply liquid to the main balancer and the sub balancer, the supplier including a passage unit supplying unit (592, 592a, 594, 594a, 596, 596a) to supply liquid to the passage unit and a sub balancer supplying unit (597, 596) to supply liquid to the sub balancer; a control unit configured to determine that the laundry causing the unbalance passes the lowest point of the drum rotation locus based on a signal of a sensing unit and to control the liquid to be supplied via the supplier to a specific one of a first passage and a second passage of the passage unit and to the sub balancer for a preset time period to damp the unbalance, wherein the sub balancer is configured to exhaust the liquid stored in the circulation passage outside the circulation passage when the rotation speed of the drum decreases.