A respiration assistance device includes a nasal respiration assisting section for supplying a gas to the nasal cavity of a living body. The nasal respiration assisting section includes: a first gas supplying portion which supplies a gas below one of the nostrils of the living body； a second gas supplying portion which supplies the gas below the other nostril of the living body； a first tube connecting portion to which a tube for supplying the gas to the first gas supplying portion is connectable； and a second tube connecting portion to which a tube for supplying the gas to the second gas supplying portion is connectable.
