Provided is a method for producing a Docetaxel polymer derivative by ester bonding any one or more of the hydroxyl groups of Docetaxel with the aspartic acid side chain carboxyl groups of a block copolymer including polyethylene glycol and polyaspartic acid. The rate of release of the Docetaxel from the Docetaxel polymer derivative so obtained is regulated by adjusting the proportion of bound Docetaxel on the block copolymer and/or the number of bonds.