An imaging device includes: a photodiode configured to perform photoelectric conversion and to generate electric charge in accordance with an amount of received light; a floating diffusion section configured to accumulate the electric charge generated in the photodiode; a reading circuit configured to output a pixel signal having a voltage in accordance with a level of the electric charge accumulated in the floating diffusion section, the reading circuit including one or a plurality of transistors each having a gate that is electrically connected to a wiring used for selecting a pixel; and an insulating section extending into part or whole of a bottom surface of the floating diffusion section, part or whole of bottom surfaces of source-drain regions in the one or the plurality of transistors, or both. The photodiode, the floating diffusion section, the reading circuit, and the insulating section are provided in a semiconductor layer.