A method of controlling a laundry treating apparatus including at least a first laundry treating device a second laundry treating device (200; 400) located below the first laundry treating device and under control of a controlling device, a water supplier having a first water pipe (313, 333) to guide water to a first tub included in the first laundry treating device, a second water pipe (317, 337) to guide water to a second tub included in the second laundry treating device, and a water control valve (315, 335) arranged at a branching point of the first water pipe (313, 333) and second water pipe (317, 337) to control the amount of water supplied to the first tub and the second tub, the method comprising: inputting information on operation in order to operate the first laundry treating device and the second laundry treating device and, supplying water to the first tub and to the second tub, wherein the supplying water to the first tub and to the second tub includes: initiating the water supply to one of the first tub and the second tub, stopping the water supply to the one of the first tub and the second tub before the water supply to the one of the first tub and the second tub is completed, initiating the water supply to the other of the first tub and the second tub, stopping the water supply to the other of the first tub and the second tub when the water supply to the other of the first tub and the second tub is completed, again supplying water to the one of the first tub and the second tub to finish the water supply to the one of the first tub and the second tub, wherein the inputting information on operation comprises inputting a command to operate the first laundry treating device and the second laundry treating device (200; 400) simultaneously, or inputting a command to operate the other of the first laudry treating device and second laundry treating device (200; 400) while the one of the the first laundry treating device and the second laundry treating device (200; 400) operates. inputting information on operation in order to operate the first laundry treating device and the second laundry treating device and, supplying water to the first tub and to the second tub, wherein the supplying water to the first tub and to the second tub includes: initiating the water supply to one of the first tub and the second tub, stopping the water supply to the one of the first tub and the second tub before the water supply to the one of the first tub and the second tub is completed, initiating the water supply to the other of the first tub and the second tub, stopping the water supply to the other of the first tub and the second tub when the water supply to the other of the first tub and the second tub is completed, again supplying water to the one of the first tub and the second tub to finish the water supply to the one of the first tub and the second tub, wherein the inputting information on operation comprises inputting a command to operate the first laundry treating device and the second laundry treating device (200; 400) simultaneously, or inputting a command to operate the other of the first laudry treating device and second laundry treating device (200; 400) while the one of the the first laundry treating device and the second laundry treating device (200; 400) operates.