PURPOSE: To obtain a block copoly-condensate that is excellent in thermal molding stability, tensile strength, and solvent-resisting properties, by incorporating a specific polyarylether sulfon block and a specific polyarylether ketone block into the copolycondensate.

CONSTITUTION: The copolycondensate comprises (A) 80 to 100 mol.% polyarylether sulfon block comprising 80 to 100 mol.% recurrent units of the formula I or nuclear-substituted 1-6C alkyl derivative, aryl derivative thereof, etc., and 0 to 20 mol.% recurring units of the formula II [X is SO3, C(CH3)2, S, O, chemical bond] or nuclear-substituted 1-6C alkyl derivative, aryl derivative thereof, etc., and (B) 2 to 25 mol.% polyaryletherketone block comprising the recurring units of the formula III [Y, T, Z are each CO, O, a CRR', chemical bond and at least one of Y, T, Z is CO; R and R' are each H, a 1-6C alkyl, etc.; (s) and (t) are each 0 or 1]. This copolycondensate has an excellent thermal molding stability, tensile strength, and solvent-resisting properties.