To provide an element integrated circuit, having a structure capable of adjusting the output from an output element, e.g. an optical integrated circuit having a structure, capable of adjusting the output from a light-receiving element.

An optical integrated circuit 10 has a photodiode 12, an output terminal 14 for outputting a signal toward outside, and a gain-adjusting circuit 16 provided between the photodiode 12 and the terminal 14, which are provided on a silicon substrate. The circuit 16 is a resistor circuit, which is reconfigured by a resistor element, which is selected from among resistor elements 18 consisting of a plurality of previously provided resistor elements connected in series, so that the circuit 16 may have a prescribed resistive value. The circuit 18 is formed, in such a way that n pieces of resistor elements R1-Rn are connected in series between an input line 22 and an output line 24 by a metal wiring 20, such as an Al wiring. If R1 and R2 are selected, the circuit 16 has a resistive value R of R=(R1×R2)/(R1+R2). When R1 and R2 are selected, the metal wiring of R3-Rn except for R1 and R2 may be cut off by a laser beam, etc.