PROBLEM TO BE SOLVED: To provide a cultivation water tank excellent in convenience and suppressed of risk causing water leakage.SOLUTION: A plurality of resin foam boards are formed into rectangular shapes, and are used as follows that: they are horizontally and vertically arranged with their side edge parts in contact with one another and are covered with a waterproof sheet in a condition where they are arranged to form at least a bottom board part of a cultivation water tank for hydroponic cultivation. A first side edge projecting part projecting outward in a planar direction is formed at the first side edge part in four side edge parts so as to be connected with one another when arranging the boards, and a second side edge recessed part engageable with the first side edge projecting part is formed at the second side edge part facing the side edge part.COPYRIGHT: (C)2014,JPO&INPIT【課題】利便性に優れ、漏水を生じるおそれの抑制された栽培水槽を提供すること。【解決手段】矩形板状に形成されており、側縁部を当接させた状態で縦横に複数配列させて用いられ、水耕栽培用の栽培水槽の少なくとも底板部を形成すべく前記配列された状態で防水性のシートが被覆されて用いられる樹脂発泡ボードであって、前記配列させるのに際して互いに連結させ得るように4つの側縁部の内の第一の側縁部には平面方向外方に突出する第一側縁突出部が形成されているとともに該側縁部と対向する第二の側縁部には前記第一側縁突出部と嵌合可能な第二側縁凹入部が形成されている樹脂発泡ボードを提供する。【選択図】図1