Abstract: Provided are a ventilation sound-diminishing apparatus and a ventilation therapy device. The apparatus comprises a sound-diminishing housing having a gas flow channel with flow channel side walls. A first flow channel side wall and a second flow channel side wall are arranged opposite to each other in a first direction. A plurality of first scattering bodies and a plurality of second scattering bodies are each arranged at intervals in a plurality of rows and columns provided on the inner surface of the side wall of the first flow channel and second flow channel, respectively. A predetermined distance is maintained between the first and second scattering bodies in the first direction. A specific frequency in a certain interval of sound wave is attenuated due to oscillation in the array structure, reducing the intensity of that frequency interval, reducing low-frequency noise in an intended elimination frequency band, and enhancing comfort of use.