An imaging device which offers an image with high quality and is suitable for high-speed operation is provided. The imaging device includes a first region to an n-th region (n is a natural number of 2 or more and 16 or less) each including a first circuit, a second circuit, a third circuit, and a fourth circuit. The first to third circuits each include a transistor in which silicon is used in an active layer or an active region. The fourth circuit includes a photoelectric conversion element and a transistor in which an oxide semiconductor is used in an active layer. The first circuit includes a region overlapping with the fourth circuit. The third circuit includes a region overlapping with the fourth circuit.