PURPOSE: To obtain a thermally stable polyamide-imide polymer which has excellent flow characteristics and can be easily processed into fibers, films, sheets, molded items, etc., by subjecting a specific arom. acid monoanhydride, an arom. acid dianhydride, and a diamine to polycondensation.

CONSTITUTION: This polyamide-imide polymer, having fluorinated linking groups, comprises repeating units represented by formula I [a and b are each the mole fraction of the corresponding repeating units in the polymer chain, and a is about 0.05-0.95 and b, about 0.95-0.05 provided a+b=1.00; n is a number high enough to give an intrinsic viscosity (0.5 wt.% concn. in dimethylacetamide, 25°C) of 0.1 dl/g; A is a divalent arom. group; and B is a tetravalent arom. group selected from among groups represented by formulas II and III]. This polymer is produced by the polycondensation of a mixture comprising 4- trimellitic anhydride chloride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 2,2-bis(3-aminophenyl)hexafluoropropane, etc.