Provided is a ventilator (1, 31) for supplying a mixed gas of oxygen and a medical gas other than oxygen to a patient as an inhalation gas (5), including a first gas supply device (2) for supplying a gas containing oxygen, an intratracheal tube path (7) inserted and placed in a trachea of the patient, an extratracheal tube path (8) for connecting the first gas supply device (2) with the intratracheal tube path (7) and guiding the gas containing oxygen from the first gas supply device (2) to the patient, and a second gas supply device (13) connected to the extratracheal tube path (8) or the intratracheal tube path (7) for supplying the mixed gas of oxygen and the medical gas other than oxygen to the extratracheal tube path (8) or the intratracheal tube path (7). Therefore, a ventilator capable of performing effective (artificial) ventilation while reducing a consumption amount of a medical gas other than oxygen is provided.
