To provide a door unlocking device which enables a door to be easily opened without causing intermeshing, even when a room interior is brought into a high pressure state by a jet of fire extinguishing gas and the like.

A latch mechanism (unlocking device) 27 includes a strike 40 which is provided on one of the opposed surfaces 21a and 22a, joined to each other, of the pair of doors 21 and 22, and a latch 35 which is provided on the other one and which can protrude from/recede into the strike 40. The latch mechanism (unlocking device) 27 is also provided with a roller 50 which abuts on the latch 35 making an entry into the strike 40 and which can be rotated in the protruding/receding direction of the latch 35.