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 5 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). 10
