A photoelectric conversion apparatus has light receiving elements disposed on an imaging plane. The light receiving element includes a plurality of photoelectric conversion portions arrayed in a first direction parallel to the imaging plane, across an isolation portion, and a light guide portion extending over the plurality of photoelectric conversion portions. In a first plane which is parallel to the imaging plane and which traverses the light guide portion, a greatest width of the light guide portion in the first direction is larger than a greatest width of the light guide portion in a second direction parallel to the imaging plane and orthogonal to the first direction.