Provided are a photodetector (PD) using a graphene thin film and nanoparticles and a method of fabricating the same. The PD includes a graphene thin film having a sheet shape formed by means of a graphene deposition process using a vapor-phase carbon (C) source and a nanoparticle layer formed on the graphene thin film and patterned to define an electrode region of the graphene thin film, the nanoparticle layer being formed of nanoparticles without a matrix material. The PD has a planar structure using the graphene thin film as a channel and an electrode and using nanoparticles as a photovoltaic material (capable of forming electron-hole pairs due to photoelectron-motive force caused by ultraviolet (UV) light). Since the PD has a very simple structure, the PD may be fabricated at low cost with high productivity. Also, the PD includes the graphene thin film to reduce power consumption.