PROBLEM TO BE SOLVED: To provide a drain device in a plant cultivation device capable of completely draining water without a troublesome work such as removal of the drain device from the plant cultivation device, when washing a nutrient water tank for storing nutrient water for water cultivation containing moisture and nutrient.SOLUTION: A drain device is configured so that: an upper flange part 13a comprises a notch-state water conduction area 15 for communicating inside and outside of a cylindrical upper cylindrical body 13； a water conduction window 16 is provided on a peripheral wall of the upper cylindrical body 13； a cylindrical inside cutoff cylindrical body 17 for closing the water conduction window 16 is fitted in the upper cylindrical body 13, and is supported by an inward protrusion 19 provided on a lower cylindrical body 12； during drainage, the water conduction window 16 is opened by detachment of the inside cutoff cylindrical body 17, then the nutrient water passes through the water conduction area 15 and the water conduction window 16 and then flows down from a drain hole 11.SELECTED DRAWING: Figure 2【課題】水分や栄養分を含む水耕栽培用養水を貯留する養水槽の洗浄等の際に、排水装置を植物栽培装置から取り外すという面倒な作業をせずに、水の完全排出を達成することができる植物栽培装置における排水装置を提供する。【解決手段】上フランジ部１３ａには円筒状の上部筒体１３の内外を連通する切欠き状通水域１５が設けられ、上部筒体１３の周壁には通水窓１６が開設され、上部筒体１３内には通水窓１６を閉じる円筒状の内部止水筒体１７が嵌め込まれて、下部筒体１２に設けられた内方突起１９で支えられており、排水時には内部止水筒体１７の抜き取りによって通水窓１６が開けられ、養水は通水域１５および通水窓１６を経て排水口１１から流下する排水装置。【選択図】図２
