The present invention relates to a methylene blue nanoparticle for bioimaging and photodynamic therapy, and a use thereof as a cancer therapeutic agent and a contrast agent. The methylene blue nanoparticle of the present invention for use as a topical cancer targeting photo therapeutic agent is composed of only a material of which the composition is clinically used or derived from human bodies, and thus a nanopreparation in which a barrier to clinical entry is low and the possibility of commercialization is very high, exhibits near-infrared fluorescence along with cancer targeting property, capacity of generating singlet oxygen and the like, and thus may be used for both bioimaging diagnosis such as optical imaging, and cancer targeting photodynamic therapy.
