PROBLEM TO BE SOLVED: To provide a hydroponic device capable of forming a peripheral environment suitable for each of an underground part and an above-ground part in each of a light period and a dark period.SOLUTION: A hydroponic device 100 includes: a ground surface part 7 which separates an underground space 16 where an underground part of a plant 1 grows, and an above-ground space 26 where an above-ground part of the plant 1 grows； a cultivation tank 6 which encloses the underground space 16 together with the ground surface part 7 and stores a nutrient solution to be supplied to the plant 1； a light emitting part 5 which is controlled to the state of the light period for irradiating light to the plant 1 and the state of the dark period without irradiating light to the plant 1； an above-ground temperature detection part 8 which detects the temperature of the above-ground space 26； a ground temperature adjustment part 90 which adjusts the temperature of the above-ground space 26； and a control part 50 which controls the above-ground temperature adjustment part 90 on the basis of information of the temperature of the above-ground space 26 detected by the above-ground temperature detection part 8, while controlling the light emitting part 5. The control part 50 controls the above-ground temperature adjustment part 90 so that the temperature of the above-ground space 26 is low, as compared to the light period, in the dark period.SELECTED DRAWING: Figure 1【課題】明期および暗期のそれぞれにおいて、地下部および地上部のそれぞれに適した周辺環境を形成し得る水耕栽培装置を提供する。【解決手段】水耕栽培装置１００は、植物１の地下部が成長する地下空間１６と植物１の地上部が成長する地上空間２６とを仕切る地表面部７と、地表面部７と一体となって地下空間１６を内包し、植物１に供給される養液を貯留する栽培槽６と、植物１に光を照射する明期の状態と植物１に光を照射しない暗期の状態とに制御される光照射部５と、地上空間２６の温度を検出する地上温度検出部８と、地上空間２６の温度を調整する地上温度調整部９０と、光照射部５を制御しながら、地上温度検出部８によって検出された地上空間２６の温度の情報に基づいて地上温度調整部９０を制御する制御部５０と、を備え、制御部５０は、暗期においては、明期に比較して、地上空間２６の温度が低くなるように、地上温度調整部９０を制御する。【選択図】図１
