An anesthetic inhalation aid device used for inhalation administration of an anesthetic in a reservoir to a patient, the anesthetic inhalation aid device comprising: a connector that is detachably and airtightly connectable to an anesthetic outlet of the reservoir; an anesthetic extraction unit connected to the connector, being in communication with the interior of the reservoir, and including an anesthetic extraction channel for unidirectionally introducing the anesthetic from the interior of the reservoir to the exterior; a mixer having an anesthetic inlet for introducing the anesthetic inward through the anesthetic extraction channel, an oxygen-containing gas inlet for unidirectionally introducing oxygen-containing gas at least containing oxygen from the exterior to the interior, a mixing chamber for mixing the introduced anesthetic with the oxygen-containing gas, and an outlet port for exhausting the mixed gas generated in the mixing chamber outward from the mixing chamber, the anesthetic inlet being formed so as to extend from the outlet port to the mixing chamber; a mixed gas introduction passage for unidirectionally introducing the mixed gas from the outlet port to the oral cavity or nasal cavity of the patient; a relief valve configured so as to open when the internal pressure of the mixed gas introduction passage reaches a level greater than or equal to a first predetermined pressure; and a remover to remove an anesthetic content in gas exhausted from the relief valve, wherein the mixer is configured as an elastic bag that can be elastically deformed by hand to increase and decrease the volume of the mixing chamber, the mixed gas being exhausted from the outlet port when the volume is decreased, and the oxygen-containing gas being introduced from the oxygen-containing gas inlet when the volume is increased. a connector that is detachably and airtightly connectable to an anesthetic outlet of the reservoir; an anesthetic extraction unit connected to the connector, being in communication with the interior of the reservoir, and including an anesthetic extraction channel for unidirectionally introducing the anesthetic from the interior of the reservoir to the exterior; a mixer having an anesthetic inlet for introducing the anesthetic inward through the anesthetic extraction channel, an oxygen-containing gas inlet for unidirectionally introducing oxygen-containing gas at least containing oxygen from the exterior to the interior, a mixing chamber for mixing the introduced anesthetic with the oxygen-containing gas, and an outlet port for exhausting the mixed gas generated in the mixing chamber outward from the mixing chamber, the anesthetic inlet being formed so as to extend from the outlet port to the mixing chamber; a mixed gas introduction passage for unidirectionally introducing the mixed gas from the outlet port to the oral cavity or nasal cavity of the patient; a relief valve configured so as to open when the internal pressure of the mixed gas introduction passage reaches a level greater than or equal to a first predetermined pressure; and a remover to remove an anesthetic content in gas exhausted from the relief valve, wherein the mixer is configured as an elastic bag that can be elastically deformed by hand to increase and decrease the volume of the mixing chamber, the mixed gas being exhausted from the outlet port when the volume is decreased, and the oxygen-containing gas being introduced from the oxygen-containing gas inlet when the volume is increased.