PURPOSE: To vary a band in a wide range by using a variable capacitor capable of generating an element value which is the multiple of reciprocal of an arbitrary integer of a basic value at a special range by the ON and OFF control of a switch and making variable a band with a digital control from an external part.

CONSTITUTION: By using a variable capacitor 13 to be able to the arbitrary reverse integer-fold element value of a basic value in the 1∼1/(2n) range by the ON the and OFF control of a switch, a band is made variable by the digital control from an external part. Thus, a variable band filter having an arbitrary integer-fold band of a basic band width can be realized in the 1∼2n-fold wide range by the digital control of an (n) bit, a non-linear distortion does not occur even due to a large amplitude action and the temperature or the change with the passage of time can be stabilized.