This study investigated the effect of artificial and natural sounds on masking of residential noises through auditory experiment. Residential noises consists of floor impact noise (children jumping) and toilet flushing noise. As masking sounds, white, pink and brown noises were used for artificial sound, and waterfall, stream, wave, rain-fall, insect and bird sounds were also included for natural sound. In the auditory experiment, thirty subjects rated preference as masking sound and annoyance (7 point verbal scale) for only residential noises and residential noise mixed with masking sounds, which have equal sound level. In addition, represented sound level of masking sounds was modified to ？3, 0 and +3 dB from original sound level, and annoyance rating experiment was repeated for the residential noises mixed with masking sounds. Results showed that stream and wave sound had the greatest masking effects for both residential noises, but insect and bird sound did not have masking effect at all. Masking sound effect was also observed for masking sound with 3 dB lower and higher sound level than residential noise. It was also found that components in middles frequency range of masking sound is important for the masking of residential noises.