A method of manufacturing photosensors is disclosed which comprises the steps of forming a photo-conductor film made chiefly of silicon and containing hydrogen on a desired substrate, forming a transparent conductive film on the photo-conductor film by sputtering, and heating the photosensor having the sputtered transparent conductive film at least at 140.degree. C. and not higher than 280.degree. C. The heat treatment is performed preferably at a temperature between 170.degree. to 250.degree. C., at which greater effect will be provided. This heat treatment remarkably improves the photo-response speed.