Provided is a method of varying the gain of an amplifying photoelectric conversion device and a variable gain photoelectric conversion device which are capable of achieving both signal processing under low illuminance and high-current processing under high light intensity, and thereby capable of securing a wide dynamic range. An amplifying photoelectric conversion part includes a photoelectric conversion element and amplification transistors forming a Darlington circuit. The sources and the drains of field-effect transistors are connected to the bases and the emitters of the amplification transistors, respectively. The gates of the field-effect transistors each function as a gain control part.