A flame-blocking nonwoven fabric has excellent processability and high flame-blocking properties. The flame-blocking nonwoven fabric has a density of 200 kg/m3 or more and includes non-melting fibers A whose high-temperature shrinkage rate is 3% or less and whose Young's modulus multiplied by the cross-sectional area of the fibers is 2.0 N or less, and thermoplastic fibers B whose LOI value is 25 or more as determined according to JIS K 7201-2 (2007).