PROBLEM TO BE SOLVED: To provide algae cultivation tools that can perform all installation operations without using a heavy machine and also can exert desired vermin damage prevention effect and further can prevent proliferation of calcareous algae, and to provide methods of cultivating large-sized algae using the algae cultivation tools.SOLUTION: A main body 2 which breeds large-sized algae, such as Fucus vesiculosus, Undaria pinnatifida, Sargassum horneri and Sargassum fusiforme, the main body 2 being provided to be a rotatable shape. The specific gravities of the body 2 is 100% or more to 140% or less of the specific gravities of the sea water of the ocean region in which the body 2 is installed, and the total mass W(g) of the body 2 is not more than the value obtained by W=2800×(1.59/γ) (γ is the specific gravity of the main body 2). A plurality of pores 3 are provided on the surface of such main body 2.SELECTED DRAWING: Figure 1【課題】全ての設置作業を重機を用いること無く実施することができ、また所望の食害防止効果を奏し得、更に石灰藻の繁殖を防止することができる藻類栽培具、及び当該藻類栽培具を用いて大型藻類を栽培する方法を提供する。【解決手段】コンブ・ワカメ・アカモク・ヒジキ等の大型藻類を繁殖させる本体２を備え、本体２は回動可能な形状になっている。また、本体２の比重は当該本体２が設置される海域の海水の比重の１００％以上１４０％以下であり、本体２の総質量Ｗ（ｇ）はＷ＝２８００×（１．５９／γ）（γは本体２の比重）によって求められる値以下である。かかる本体２の表面には複数の細孔３が設けてある。【選択図】図１
