The interior of a fractionating tool for fractionating dioxins is packed with a purification layer and an adsorption layer. The adsorption layer includes a first adsorption layer including an activated carbon-containing silica gel layer and a graphite-containing silica gel layer, and a second adsorption layer including an alumina layer. When a solution of dioxins is injected into the purification layer and is supplied with an aliphatic hydrocarbon solvent, the solvent dissolves dioxins in the solution of dioxins and passes through the purification layer and the adsorption layer. In this process, non-ortho PCBs, PCDDs and PCDFs among dioxins are adsorbed to the first adsorption layer, and mono-ortho PCBs among dioxins are adsorbed to the second adsorption layer. As a result, dioxins are fractionated into a group including non-ortho PCBs, PCDDs and PCDFs, and mono-ortho PCBs.