A hydroponic cultivating device includes a first spraying portion configured to supply a plant with water utilizing electric power; a second spraying portion configured to supply the plant with the water utilizing water-line pressure; a detecting portion configured to detect a state of electric power supply necessary for supplying the plant with the water by the first spraying portion; and a controlling portion configured to control the second spraying portion, wherein the controlling portion switches a city-water switching valve and a discharge switching valve from a closed state to an open state, and thereby, supplies the plant with the water by the second spraying portion, 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.
