A respiratory assistance apparatus guides gas from a gas supply source to a connection part via an inspiratory pathway. A check valve that allows the gas from the gas supply source to pass to the connection part side and prevents exhaled air discharged from the nose or mouth from flowing into the gas supply source side is arranged on the inspiratory pathway. An expiratory valve is arranged on the inspiratory pathway closer to the connection part than the check valve is, and the expiratory valve is opened to discharge the exhaled air from the inspiratory pathway during expiration. This eases a respiratory load on the patient and reduces contamination of the apparatus.
