The invention relates to a photoelectric conversion device and an imaging system. The photoelectric conversion device includes a photoelectric conversion element including a first semiconductor region of a first conductivity type, a second semiconductor region of the first conductivity type provided in contact with the first semiconductor region, a third semiconductor region of the first conductivity type provided apart from the second semiconductor region, a fourth semiconductor region of a second conductivity type provided between the second and the third semiconductor region, and a fifth semiconductor region of the first conductivity type provided apart from the third semiconductor region, wherein an impurity concentration of the third semiconductor region is lower than that of the fifth semiconductor region, and a depth of a lower-edge of the third semiconductor region from a surface of the semiconductor substrate is larger than that of a lower-edge of the fifth semiconductor region.