PROBLEM TO BE SOLVED: To provide a hydroponic device for cultivating plants, including two separate circulation passages for circulating nutrient solutions of different compositions in accordance with growth of plants on a hydroponic rack unit, so that the two circulation passages are switched for use so as to circulate nutrient solution of different component composition. SOLUTION: The hydroponic device includes the cultivation rack unit 3 equipped with a plurality of cultivation racks 2 on which cultivation rack tanks 1 can be placed for hydroponics of plants, a first nutrient solution supply system 4 to supply and circulate a first nutrient solution of different component composition to the cultivation rack tank 1 on the cultivation rack unit 3, and a second nutrient solution supply system 5 to supply and circulate a second nutrient solution of different component composition to the cultivation rack tank 1 on the cultivation rack unit 3. The two separate circulation passages are thus formed for circulating the first nutrient solution or the second nutrient solution to the cultivation rack unit 3 for hydroponics, so that the two circulation passages are switched in accordance with growth of plants. COPYRIGHT: (C)2012,JPO&INPIT
