The purpose of the present invention is to provide a hydrogen mixed gas supply device capable of administering a mixed gas having the hydrogen gas concentration and the oxygen gas concentration thereof each appropriately adjusted in accordance with the condition of a patient. This hydrogen mixed gas supply device is used for the treatment of patients and is characterized by comprising: a hydrogen supply means being the supply source for the hydrogen； an oxygen supply means being the supply source for the oxygen； a mixing means that generates a mixed gas including the hydrogen and the oxygen； a hydrogen gas concentration measurement means that measures the hydrogen gas concentration in the mixed gas； an oxygen gas concentration measurement means that measures the oxygen gas concentration in the mixed gas； and a control means that controls to any value both the hydrogen gas concentration and the oxygen gas concentration of the mixed gas, on the basis of the hydrogen gas concentration and the oxygen gas concentration measured by the measurement means.
