PURPOSE: To decrease a cost and to minimize the error of an increasing and decreasing quantity in a boosting direction and a cutting direction by using the same resistance group in the boosting direction and the cutting direction and changing over the resistance group with an analog switch in accordance with the boosting direction and the cutting direction.

CONSTITUTION: When a volume control signal CB is supplied to an analog switch control circuit 14 and decided to be a boosting direction, analog switches SW14 and SW17 come to be on and SW15 and SW16 come to be off. Consequently, a resistance R1 is connected to an input terminal 11 and a resistance R13 is connected to a terminal 12 respectively and comes to be a boosting mode. In such a condition, when one analog switch out of analog switches SW1∼SW7 is selected by the output of the analog switching control circuit 14 and comes to be on, an output signal Dout of the boosting direction is obtained which the time when the analog switch SW7 is selected is made into a reference (0dB). On the other hand, in case of the cutting direction, the analog switches SW15 and SW16 come to be on, the SW14 and SW17 come to be off, and the resistance R13 is connected to the terminal 12 and the resistance R13 is connected to the input terminal 11. Thus, a cutting mode is obtained.