An imaging device includes a first substrate including a photoelectric conversion layer that includes a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type and in which a plurality of photoelectric conversion units are provided; a second substrate that is joined to the first substrate and in which a readout circuit substrate that outputs a signal based on information detected by the plurality of photoelectric conversion units is provided; and an element isolation portion defined by a first opening provided so as to penetrate the second substrate and at least one of the first semiconductor layer and the second semiconductor layer, and each of the plurality of photoelectric conversion units is separated from each other by the element isolation portion.