A method of manufacturing a photoelectric conversion device having a semiconductor substrate, comprises a first step of forming an insulating film on the semiconductor substrate, a second step of forming first holes in the insulating film, a third step of forming, in the insulating film, second holes shallower than the first holes, a fourth step of forming electrically conductive portions by embedding an electrically conductive material in the first holes, and forming planarization assisting portions by embedding the electrically conductive material in the second holes, and a fifth step of polishing the electrically conductive portions, the insulating film, and the planarization assisting portions until the planarization assisting portions are removed, thereby planarizing upper surfaces of the electrically conductive portions and the insulating film.