An apparatus for reducing noise component contained in an input signal has: a detecting device for detecting a level of the noise component; an adjusting device for adjusting a level of the input signal so as to make the level of the noise component equal to or lower than a predetermined threshold level; a reducing device for reducing a signal component of the adjusted input signal whose level is equal to and lower than the predetermined threshold level; and a restoring device for restoring a level of the adjusted input signal to the level of the input signal that has not been adjusted by the adjusting device yet.