To provide a flame-retardant sealing material having a high flame- retardancy, reduced a smoking property, and excellent sealability.

This flame-retardant sealing material A has a flame-retardant treatment layer 2 on the front face of a base fabric 1 and a flame-retardant rubber coating layer 3 on the reverse face thereof, wherein (a) the flame- retardant treatment layer 2 comprises butyl rubber with or without polyisobutylene, aluminum hydroxide, ammonium polyphosphate (APP), pentaerythritol, a phosphate ester-based flame retardant, carbon, a tackifier, and a vulcanizing agent, and (b) the flame-retardant coating rubber layer 3 comprises the polyisobutylene, polybutene, the aluminum hydroxide, a silicone- based flame retardant, the carbon, and the vulcanizing agent.