Imaging devices with increased numbers of parallel analog-digital converters with maintained chip size are disclosed. In one example, an imaging device has a stacked chip structure including semiconductor chips of first through third layers. A pixel array is formed on the semiconductor chip of the first layer. An analog circuit of an analog-digital converter is disposed on the semiconductor chip of the second or third layer. A digital circuit of the analog-digital converter is disposed on the other of the semiconductor chip of the second or third layer.