PURPOSE: To obtain a polycyanoaryl ether useful for electronic and precision machines, etc., with a low frequency of washing and a small amount of waste water according to a method for producing the polycyanoaryl ether gentle to the environment by separating and removing a by-product salt from a polymer solution prepared by carrying out the polycondensation of a dihalogenobenzonitrile with a dihydric phenol while the polymer solution is hot.

CONSTITUTION: The polycondensation of (C) a dihalogenobenzonitrile (e.g. 2,6- dichlorobenzonitrile) with (D) a dihydric phenol (e.g. resorcin or hydroquinone) is carried out in the presence of (A) an alkali metallic salt [e.g. sodium (hydrogen)carbonate or potassium carbonate] and (B) a polymerization solvent (e.g. N-methyl-2-pyrrolidone). A by-product salt in the resultant high-molecular weight polycyanoacryl ether solution at 50-200g/l polymer concentration and 100-210°C solution temperature is separated and removed from the solution by filtration, separation by allowing to stand still or centrifugation to afford the objective polymer.