A hydroponic system (1) using seawater, wherein seawater (W1) is used for hydroponic cultivation of salt-tolerant plants, including a water supply pump (21) that pumps up, from the sea (S), seawater (W1) having a salinity, a bacteria content and an unwanted matter content are less than or equal to predetermined threshold values； a water tub (30) that stores seawater (W1) pumped up by the water supply pump (21) and accommodates salt-tolerant plants (P) to be cultivated； and a filter (27) that removes bacteria and unwanted matter from the seawater (W1) obtained from the sea (S)； wherein the seawater (W1) from which the bacteria and the unwanted matter have been removed by the filter (27) is fed to the water tub (30).
