Photodetector 1 is equipped with photodiodes PDn, integrating circuits 10n, CDS circuits 20n, and hold circuits 30n. Each integrating circuit 10n includes an amplifier 11n, a capacitor C, and a switch SW. Photodiodes PDn are aligned on a first substrate 100. A differential pair input part (transistors T.sub.1 and T.sub.2) of amplifier 11n, capacitor C, etc., of each integrating circuit 10n are disposed on a second substrate 200. A drive part (transistors T.sub.5 and T.sub.6) of amplifier 11n, etc., of each integrating circuit 10n are disposed on a third substrate 300.