An intermittent supply of ozonated water to underground roots revealed a promotive effect on the growth of komatsuna (Brassica rapa var. perviridis). Although no clear difference in germination time and early growth was seen, a definite difference appeared ~27d after germination. A remarkable difference was observed in growth rate after 49 d, whereas growth rate in the control was nearly saturated. Plant weight after 49 d increased by 2–3 times, compared to that of the control. An intermittent supply of a suitable amount of ozonated water to the underground soil increased plant growth promotion.