The present invention relates to: a conjugate for photodynamic diagnosis or therapy, in which folic acid is coupled to a photosensitizer or a near-infrared fluorescent dye through an intracellular cleavable link and a composition for photodynamic diagnosis or therapy, containing the same. In the present invention, folic acid functions as a target ligand for cells, overexpressing a folic acid receptor, and quenches the optical properties of a fluorescent dye and a photosensitizer. A fluorescent signal and reactive oxygen are not generated from a fluorescent dye and a photosensitizer by the quenching action of folic acid when a conjugate of folic acid and a fluorescent dye or a photosensitizer is formed through a cleavable linker having a length of 0.5-10 nm. Folic acid can no longer function as a quencher after the conjugate is specifically taken into cells overexpressing a folic acid receptor, a linker of the conjugate is decomposed by an endoenzyme, a reducing agent or a low pH environment, and the distance between folic acid and a fluorescent dye or a photosensitizer increases, and thus a strong fluorescent signal can be generated and photodynamic therapy effects are also exhibited from this point on. The conjugate for photodynamic diagnosis or therapy, containing folic acid, according to the present invention has high tissue permeability, is safe in normal cells but exhibits high treatment effects only in target cells (for example, cancer cells), and allows a good diagnostic image having a high signal-to-background ratio to be obtained through the quenching function of folic acid.La présente invention concerne : un conjugué pour diagnostic ou thérapie photodynamique, dans lequel de lacide folique est couplé à un photosensibilisateur ou un colorant fluorescent dans le proche infrarouge à travers une liaison intracellulaire clivable et une composition le contenant, pour diagnostic ou thérapie photodynamique. Selon la présente invention, lacide folique fonctionne c
