A laundry treating device includes two separate laundry washing mechanisms. Methods of controlling such a laundry treating device include steps for 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. The water can be supplied to the two tubs simultaneously or separately. Also, the water supply steps can be alternated. Further individual hot and cold water supply steps can include simultaneously or sequentially supplying the hot and cold water.