A taxane-containing amphiphilic block copolymer micelle composition, including taxane, an amphiphilic block copolymer containing a hydrophilic block and a hydrophobic block, and an osmolality adjusting agent, is described. Also described are a method for preparing the same composition. The composition has excellent stability so that it can prevent rapid release of a drug and can improve a desired pharmacological effect. Additionally, the method enables highly efficient preparation of the composition.