In a masking sound generating apparatus, a band divider divides a target sound signal into a plurality of frequency bands to generate a plurality of band signals. An envelope signal generating part generates a plurality of envelope signals representing respective envelopes of the plurality of the band signals. A signal converter segments each of the plurality of the envelope signals into a plurality of frames, then specifies frames of segmented envelope signals which have an amplitude greater than a first threshold and less than a second threshold, and changes an order of the specified frames in an arrangement of the plurality of the frames. A multiplier multiplies each of the plurality of the envelope signals by a noise signal, each envelope signal having the order of the frames changed by the signal converter, and outputs the plurality of the envelope signals multiplied by the noise signal as individual band masking signals. An adder adds the individual band masking signals to output a masking sound signal capable of masking the target sound signal.