A photoelectric conversion device comprising: a plurality of photoelectric conversion units which are arranged in a semiconductor substrate; a first insulation film which is directly arranged on the photoelectric conversion units; a second insulation film which is directly arranged on the first insulation film, the first insulation film and the second insulation film constituting a first antireflection portion on the photoelectric conversion units; and an element isolation portion which is arranged in an element isolation region in the semiconductor substrate so as to electrically isolate the plurality of photoelectric conversion units and which includes an insulator; a semiconductor region which is arranged in a region adjacent to the element isolation portion in the semiconductor substrate, a third insulation film which is directly arranged on the element isolation portion, a refractive index of the third insulation film being equal to a refractive index of the second insulation film, the element isolation portion and the third insulation film constituting a second antireflection portion on the element isolation region, an interlayer film which is arranged on the third insulation film, wherein the refractive index of the second insulation film and the third insulation film is higher than a refractive index of the first insulation film and a refractive index of the insulator and less than a refractive index of the plurality of photoelectric conversion units and a refractive index of the semiconductor region, characterized in that a thickness of the third insulation film being effective to set a reflectance in the element isolation portion lower than a reflectance in the element isolation portion in a case of forming the third insulation film on the element isolation portion at the same thickness as a thickness of the second insulation film, wherein the reflectance in the element isolation portion is a ratio of light reflected to the interlayer film to light having passed through the interlayer film and entering the element isolation portion. a plurality of photoelectric conversion units which are arranged in a semiconductor substrate; a first insulation film which is directly arranged on the photoelectric conversion units; a second insulation film which is directly arranged on the first insulation film, the first insulation film and the second insulation film constituting a first antireflection portion on the photoelectric conversion units; and an element isolation portion which is arranged in an element isolation region in the semiconductor substrate so as to electrically isolate the plurality of photoelectric conversion units and which includes an insulator; a semiconductor region which is arranged in a region adjacent to the element isolation portion in the semiconductor substrate, a third insulation film which is directly arranged on the element isolation portion, a refractive index of the third insulation film being equal to a refractive index of the second insulation film, the element isolation portion and the third insulation film constituting a second antireflection portion on the element isolation region, an interlayer film which is arranged on the third insulation film, wherein the refractive index of the second insulation film and the third insulation film is higher than a refractive index of the first insulation film and a refractive index of the insulator and less than a refractive index of the plurality of photoelectric conversion units and a refractive index of the semiconductor region,