PROBLEM TO BE SOLVED: To provide a novel hydroponics means which can enlarge a harvesting part of a root of a root crop.SOLUTION: The hydroponics system A for root crops includes: a cultivation tank 1 for storing a nutrient fluid W； cylindrical parts 3 formed in the vertical direction within the cultivation tank 1； and a level varying means 4 for varying the level of the nutrient fluid W within the cultivation tank 1. Harvests of axial roots can be obtained by forming the cylindrical parts 3 in the vertical direction within the cultivation tank 1. Furthermore, by varying the level of the nutrient fluid W within the cultivation tank 1, the harvesting parts of the roots can be sufficiently enlarged. For example, a settled planting structure 2 formed of a lightweight member, floating in the nutrient fluid W is set in the cultivation tank 1, and by moving the settled planting structure 2 downward, the level of the nutrient fluid W is varied. For example, a linear member 43 is laid in the settled planting structure 2, and by taking up the linear member 43, the settled planting structure 2 can be moved downward.
