To provide a heat resistant filter material easy for forming dense nonwoven fiber assembly, having high dust collecting capacity with little pressure loss, and excellent heat resistance and chemical stability.

Fiber layers containing 20 wt.% or more of ultrafine fiber with an arrangement fineness of 1.0 decitex or less consisting of aromatic polyimide fiber are laminated on both sides or on one side of a base cloth, which is subjected to needle punching processing for forming entangled nonwoven fabric, followed by heat treatment at 300°C or higher. Coating of a heat-resistant binder on the surface or whole the face of the fiber layer containing the ultrafine fiber of aromatic polyimide fiber is further effective.