PROBLEM TO BE SOLVED: To reduce a generation of waste by readily separating a root from a medium, to allow reuse of the medium by a low propagation of saprophyte or the like, and to readily form an air space for root respiration in relation to a hydroponics technology for cultivating a plant with a resin culture medium.SOLUTION: A container body 11 of a hydroponic device 10 contains a polymer foam 12 which has open cells and is cut into a contour having a size of 0.3 cm x 5.0 cm. A medium 13 is injected into a container body 11 to soak the polymer foam 12 and subsequently the medium 13 is discharged. A process where air spaces are formed between the polymer foams 12 while the medium is soaked in the open cells of the polymer foam 12 is repeatedly carried out.【課題】植物を樹脂培地で育成する養液栽培技術に関し、収穫後に根と培地の分離が容易で廃棄物の発生を激減させること、雑菌等の繁殖が少なく繰り返し使用でること、根の呼吸を担う空気層が容易に得られること、を課題とする。【解決手段】養液栽培装置１０の容器本体１１に外形が０．３ｃｍ～５．０ｃｍの大きさにカットした連続気泡を有する高分子発泡体１２を収容し、容器本体１１に培養液１３を注入して高分子発泡体１２を浸してから排出し、高分子発泡体１２の連続気泡に培養液をしみ込ませるとともに高分子発泡体１２どうしの間に空隙を形成する工程を、繰り返し行うこととした。【選択図】図１
