A cannula device which supplies respiration gas to a patient provided with: a nasal cannula including nasal pipes inserted into nares of the patient a pair of supplying tubes connected to both ends of the nasal cannula respectively a bracket provided at at least one of the nasal cannula or the supplying tubes and a locking part provided at the bracket, and detachably locking a fixture which attaches the nasal cannula on a head of the patient.
