Disclosed is an avalanche photodiode using a silicon nanowire, including a first silicon nanowire formed of silicon (Si), a first conductive region formed by doping one surface of the first silicon nanowire with a first dopant, and a second conductive region formed by doping one surface of the first silicon nanowire with a second dopant having a conductive type different from that of the first dopant so as to be arranged continuously in a longitudinal direction from the first conductive region, wherein, when the magnitude of a reverse voltage applied to both ends of the first silicon nanowire is equal to or greater than a preset breakdown voltage, avalanche multiplication of inner current occurs due to the incidence of light from the outside.