A method for manufacturing a photoelectric conversion device comprising the steps of fixing a first substrate including a semiconductor layer provided with a photoelectric conversion element, to a second substrate, thinning the first substrate fixed to the second substrate, from the opposite side of the first substrate from the second substrate, fixing the first substrate to a third substrate provided with a semiconductor element such that the third substrate is located on the opposite side of the first substrate from the second substrate, and removing the second substrate after the step of fixing the first substrate to the third substrate.