To provide a fire-proof damper for a ventilation ridge laid on the roof of a building so as to cover a ventilation space in the building, which is adapted to be incorporated in the ventilation ridge, and which has a simple structure so as to prevent ventilation between the inside and outside of the building from being obstructed.

A protrusion 41 of a leaf spring 4 is usually brought into contact with a fuse 32 of a projecting piece 3. The spring 4 is resiliently biased toward in a separating direction, having a lower end side engaged with a locking panel 5 so as to hold a cover panel 2 which is therefor pressed upward above a laid panel 1. With this arrangement, when the fuse 32 is melted, the protrusion 41 of the leaf spring 4 is projected into an opening formed in the projecting piece 3 so as to resiliently displaced toward the planar surface of the projecting piece 3, and the leaf spring 4 is disengaged from the locking panel 5 so as to make the cover panel 2 into press contact with the laid panel 1, thereby it is assembled so as to block a ventilation hole 10a.