The present invention relates to a conjugate of acetylated biocompatible polysaccharide and phthalocyanine-based compound for photodynamic diagnosis or therapy in which biocompatible polysaccharide is acetylated and a phthalocyanine-based compound is bound to the acetylated polysaccharide. The conjugate for photodynamic diagnosis or therapy according to the present invention is characterized in that the polysaccharide is acetylated to improve solubility in a solvent and thus enable various chemical modifications, and the conjugate may specifically target tumor cells, has superior cancer cell selecting and accumulating capacity, and has excellent effects of killing cancer cells when near infrared ray is irradiated. The conjugate of the present invention may not show cytotoxicity for cells other than cancer cells even when near infrared ray is irradiated, and thus exhibits superior in vivo stability, and therefore, may be valuably used in disease diagnosis or therapy using photodynamics.
