A polylactide derivative according to the present invention is expressed by the following general formula (1) or general formula (2): In general formula (1), one of X1-X5 is an aldehyde group, one of the other four is an alkoxy group, and the other three are hydrogen atoms. In general formula (2), one of R1-R3 is selected from a chlorine atom, fluorine atom, aldehyde group, alkoxy group, alkyl group and ester, while the other two are selected from the chlorine atom, fluorine atom, aldehyde group, alkoxy group, alkyl group, ester, and hydrogen atom.