To constitute an air supply device capable of inhibiting the spread of a fire at a time when the fire is generated in a tunnel for a magnetically levitated type railway.

The tunnel for the magnetically levitated type railway, in which a single or a plurality of guide ways are laid and to which a track device consisting of ground coils covered with insulating members arranged to the internal surfaces of the side sections of the above-mentioned guide ways and feeder cables being laid on the bottom sections of the above-mentioned guide ways and supplying the above-mentioned ground coils with a current is arranged, is partitioned into a plurality of exhaust control sections by installing noncontact type partition means 21 at every fixed length. The air supply devices 25 having nitrogen-gas mixing means are mounted at every section, and nitrogen gas is mixed with the outside air and air supply is conducted so that the oxygen concentration of air in the tunnel reaches 18% or more and reaches oxygen concentration of the lowest oxygen exponent or less of each insulating member constituting the track device by the above-mentioned nitrogen-gas mixing means of the air supply devices 25.