This hydroponic system (1) uses seawater (W1) for hydroponically cultivating salt-resistant plants and is provided with: a water supply pump (21) for pumping from the sea (S) seawater (W1) having a salt concentration, bacterial content and unwanted matter content which are not more than predetermined reference values; a water tank (30) which stores the seawater (W1) pumped by the water supply pump (21) and in which a salt-resistant plant (P) to be cultured is placed; and a filter (27) for removing bacteria and unwanted matter in the seawater (W1) taken from the sea (S). The hydroponic system (1) is configured so that the seawater (W1) from which the bacteria and unnecessary matter have been removed by the filter (27) is delivered to the water tank (30).
