The present invention relates to a photodetector using nanoparticles, and more particularly, to a novel photodetector wherein surfaces of nanoparticles synthesized by a wet colloidal process are capped with organic materials which then serve as channels for electron migration, or nanoparticles, from which organic materials capped on the surfaces of nanoparticles are removed to form a close-packed particle structure, directly serve to transport electrons. In accordance with specific embodiments of the present invention, it is possible to improve performance of the photodetector and simplify the manufacturing process thereof.