A semiconductor integrated circuit comprising: a first semiconductor substrate in which a part of an analog circuit is formed; a second semiconductor substrate in which the remaining part of the analog circuit and a digital circuit are formed, wherein the remaining part of the analog circuit includes a transistor which has a gate connected to a bias supply; and a substrate connection portion which connects the first and second semiconductor substrates (51, 53) to each other, wherein the substrate connection portion is configured to transmit an analog signal which is generated by the part of the analog circuit of the first semiconductor substrate to the second semiconductor substrate, wherein the semiconductor integrated circuit further includes a plurality of photoelectric conversion elements configured to generate a charge, a transmission portion configured to transmit the charge generated by the plurality of photoelectric conversion elements, and a conversion portion configured to convert the charge transmitted by the transmission portion into a digital signal, the plurality of photoelectric conversion elements are formed as the part of the analog circuit in the first semiconductor substrate, the conversion portion is formed as the digital circuit in the second semiconductor substrate, and the transmission portion includes the substrate connection portion and is formed from the first semiconductor substrate to the second semiconductor substrate. a first semiconductor substrate in which a part of an analog circuit is formed; a second semiconductor substrate in which the remaining part of the analog circuit and a digital circuit are formed, wherein the remaining part of the analog circuit includes a transistor which has a gate connected to a bias supply; and a substrate connection portion which connects the first and second semiconductor substrates (51, 53) to each other, wherein the substrate connection portion is configured to transmit an analog signal which is generated by the part of the analog circuit of the first semiconductor substrate to the second semiconductor substrate, wherein the semiconductor integrated circuit further includes a plurality of photoelectric conversion elements configured to generate a charge, a transmission portion configured to transmit the charge generated by the plurality of photoelectric conversion elements, and a conversion portion configured to convert the charge transmitted by the transmission portion into a digital signal, a plurality of photoelectric conversion elements configured to generate a charge, a transmission portion configured to transmit the charge generated by the plurality of photoelectric conversion elements, and a conversion portion configured to convert the charge transmitted by the transmission portion into a digital signal, the plurality of photoelectric conversion elements are formed as the part of the analog circuit in the first semiconductor substrate, the conversion portion is formed as the digital circuit in the second semiconductor substrate, and the transmission portion includes the substrate connection portion and is formed from the first semiconductor substrate to the second semiconductor substrate.