To provide a hydroponic culture system whereby the initial cost and the running cost can be controlled each at a low level in growing plants and plants having excellent qualities can be obtained at a high productivity. In a culture room (1), culture container units (2), each having a plurality of lighting fixtures (4) attached to the lower face of the bottom wall (3a) of a culture container (3) in which a nutrient solution (L) is pooled, are located at multiple stages at definite intervals in the longitudinal direction. On the other hand, the nutrient solution (L) is circulated between a nutrient solution tank (25) and the solution containers (3) in the individual culture container units (2). In the pathway of the circulation of the nutrient solution (L), a cooling unit (27) is provided and the culture container units (2) so that the nutrient solution (L) refluxed from the individual solution containers (3) is subjected to radiation cooling and then supplied into the individual solution containers (3). Owing to this constitution, a portion of the heat from the side of the lighting fixtures (4, 4) is absorbed by the nutrient solution (L) via the bottom wall (3a) of the culture containers (3). Thus, the heat to be transferred to the plants (11) in the culture container unit (2) on the next lower stage is decreased by the thus absorbed heat amount and the effect of the heat on the plants (11) is reduced. As a result, the interval between the culture container unit (2) on the upper stage and the culture container unit (2) on the lower stage can be narrowed and thus the number of the stages can be increased, which enables more efficient utilization of the space.