Abstract: Due to a constantly increasing world population, a decrease of farm land, climate changes and food safety concerns, many companies have gotten involved in plant factories that grow certain crops regardless of the weather of environment. In the plant factory, the growing environment can be controlled and the crop can also be controlled. As one of control factors, this study studies the effects on lettuce growth which varies considerably by LED light intensity along the distance. For showing the effects, lettuce production in the plant factory is compared and analyzed.