There is provided a variable RF filter receiving an input differential radio frequency signal from a differential input terminals (501, 502) and allowing a radio frequency signal around a desired frequency to pass therethrough, wherein first passive mixers (901, . . . , 904) driven by a rectangular wave clock signal having an arbitrarily determined frequency are connected in parallel to a signal line across the differential input terminals (501, 502) and differential output terminals (918, 919), and wherein a load of each of the first passive mixers (901, . . . , 904) is configured by inductors (903, . . . , 906). Further, as a clock signal driving each of the first passive mixers (901, . . . , 904), an odd-multiple-wave Lo signal (for example, a triple-wave Lo signal) is used, the signal having a frequency odd-multiple times (for example, three times) as high as that of the Lo signal which is the fundamental wave of the passing radio frequency signal.