Abstract: A hydroponic cultivation kit enables taking a plant seedling, intact in its planting soil, out of a growth pot and replanting it. Within a growth pot prepared in advance, a plant seedling or the like planted in soil is taken out of the growth pot together with the soil and cultivated in a culture solution. The hydroponic cultivation kit is furnished with: foam stone for surrounding the soil periphery of the plant taken out from the growth pot; a retaining mesh pot for retaining the plant with its soil periphery surrounded by the foam stone; and a buoyant member for floating the mesh pot in culture solution inside a water-tank unit. The mesh pot has perforations such as to prohibit the foam stone from passing through it, yet meanwhile permit passage of roots jutting out from the plant.