To provide a tunnel fire extinguisher apparatus permitting easy attachment of an ID tag to a fire extinguisher securing the resistance against highly corrosive exhaust gas or dust, and securing excellent radio properties.

A tunnel hydrant apparatus 10 as the tunnel fire extinguisher apparatus including a fire extinguisher door 28 on the front surface of a casing, in which a fire extinguisher 60 is housed, includes: a transparent electromagnetic wave transmitting window 30 disposed in the fire extinguisher 60 for transmitting electromagnetic waves; and a tag device 50 detachably attached to the fire extinguisher 60 at a position facing the electromagnetic wave transmitting window 30 by a fixing member in such a state that a tag storing identification information is stored under a tag cover. Presence of the fire extinguisher is confirmed by reading information from the tag of the fire extinguisher 60 by a reader mounted on a vehicle travelling inside a tunnel.