A method of controlling a laundry treating apparatus including a first laundry treating device and a second laundry treating device (200; 400) adjacent to the first laundry treating device, under control of a controlling device, the method comprising: a step of inputting information to the controlling device to operate one or both of the first laundry treating device and the second laundry treating device (200; 400), and a step of supplying water to a first tub provided in the first laundry treating device and to a second tub provided in the second laundry treating device (200; 400), wherein the step of inputting information comprises: inputting a command to operate both of the first laundry treating device and second laundry treating device (200; 400) or inputting a command to operate the other of the first laundry 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, wherein the step of supplying water includes supplying water both to the first tub and to the second tub concurrently after the inputting the command to operate both of the first laundry treating device and second laundry treating device (200; 400), or after the inputting the command to operate the other of the first laundry treating device and second laundry treating device (200; 400). a step of inputting information to the controlling device to operate one or both of the first laundry treating device and the second laundry treating device (200; 400), and a step of supplying water to a first tub provided in the first laundry treating device and to a second tub provided in the second laundry treating device (200; 400), wherein the step of inputting information comprises: inputting a command to operate both of the first laundry treating device and second laundry treating device (200; 400) or inputting a command to operate the other of the first laundry 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, wherein the step of supplying water includes supplying water both to the first tub and to the second tub concurrently after the inputting the command to operate both of the first laundry treating device and second laundry treating device (200; 400), or after the inputting the command to operate the other of the first laundry treating device and second laundry treating device (200; 400). inputting a command to operate both of the first laundry treating device and second laundry treating device (200; 400) or inputting a command to operate the other of the first laundry 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, wherein the step of supplying water includes supplying water both to the first tub and to the second tub concurrently after the inputting the command to operate both of the first laundry treating device and second laundry treating device (200; 400), or after the inputting the command to operate the other of the first laundry treating device and second laundry treating device (200; 400).