PURPOSE: To obtain the gain control circuit whose input/output impedance is constant and whose frequency amplitude characteristic is flat within a prescribed frequency band.

CONSTITUTION: In the gain control circuit in which one or over of variable resistive elements 1-3 whose resistance changes with an applied voltage are connected in a form of π, a varactor element 20 is connected in series or parallel with the variable resistive elements to change the capacitance of the varactor element 20 with a voltage controlling the resistance of the variable resistive elements. Thus, the input/output impedance is compensated and the frequency amplitude characteristic within a frequency band is made flat. Furthermore, at least the parallel connection of two variable resistive elements 1, 30 is adopted for the variable resistive elements connecting in series with the strip line from an input terminal to an output terminal to reduce the insertion loss.