A method of manufacturing a photo sensor includes forming a first conductive layer on a substrate, the first conductive layer including a metal layer and a transparent conductive oxide layer formed on the metal layer, forming a photoconductive layer on the first conductive layer, forming a second conductive layer on the photoconductive layer, forming a first photoresist pattern on the second conductive layer, etching the second conductive layer using the first photoresist pattern as an etch mask to form a second electrode, deforming the first photoresist pattern to form a second photoresist pattern, and etching the photoconductive layer and the first conductive layer using the second photoresist pattern to form a photoconductive pattern and a first electrode, respectively.