To provide a flameproof shutter for fire spread prevention which retains a ventilation function without impairment during the normal time and is capable of effectively shielding vent structure parts, such as vent layers, in the event of the outbreak of a fire.

The flameproof shutter 1 consists of heat resistant base plates 2 which have many vent holes 20 and are mounted in the state of partitioning the vent structure parts and foamable fire resistant coating materials 3 which are applied on these base plates 2 in the state of not closing the vent holes 20. The vent holes 20 are made closable by the thermal expansion of the foamable fire resistant coating materials 3 at a prescribed temp. or above by regulating the sizes of the vent holes and the coating thickness of the foamable fire resistant coating materials 3.