To make nearly constant the quantity of variation in reflection coefficient with a control voltage over the entire control range by connecting variable resistance elements in parallel, setting both the ends as an input terminal and an output terminal, and controlling each variable resistance element according to controlled variables obtained by weighting a control variables inputted from one control terminal as specified respectively.

The variable resistance elements 1-1 to 1-n are connected in parallel; and one end is used as the input terminal and the other end is used as the output terminal. The respective variable resistance elements are controlled according to the control variables obtained by weighting the control variable inputted from one control terminal by specific weights W1 to Wn. At this time, the weights W1 to Wn corresponding to the respective variable resistance elements are optimized and the quantity of variation in reflection coefficient with the controlled variable when the output terminal is grounded can be made nearly constant. This variable resistance circuit is used to make nearly constant the quantity of variation in passage attenuation with the control voltage.