A hydroponic cultivating device includes a first spraying portion (13A) configured to supply a plant with water utilizing electric power a second spraying portion (13B) configured to supply the plant with the water utilizing water-line pressure a detecting portion (52) configured to detect a state of electric power supply necessary for supplying the plant with the water by the first spraying portion (13A) and a controlling portion (51) configured to control the second spraying portion (13B), wherein the controlling portion (51) switches a city-water switching valve (72) and a discharge switching valve (81) from a closed state to an open state, and thereby, supplies the plant with the water by the second spraying portion (13B), in a case where it is determined that the electric power supply is stopped, based on the state of the electric power supply detected by the detecting portion (52).
