PURPOSE:To perform efficient condensation treatment without stripping gas pressure raising. CONSTITUTION:A stripping gas containing a monovalent phenol compound, bisphenol compound and steam 3 is maintained under a reduced pressure of =30Torr and under such temperature conditions as to maintain the steam in a gaseous state and part of the monovalent phenol compound in a liquid state, and put to counter current contact with the first cooling medium 5 comprising the monovalent phenol compound or its mixture with the bisphenol compound to effect condensation of the virtually whole quantity of the bisphenol compound in said stripping gas and part of the monovalent phenol compound, and obtaining a mixed gas 8 of uncondensed steam and the monovalent phenol compound. Said mixed gas 8 is then put to counter current contact with the second cooling medium 9 comprising an aqueous solution of the monovalent phenol compound under a reduced pressure of =30Torr and under such temperature conditions as to condense the virtually total quantity of said mixed gas 8 to effect condensation of the virtually total quantity of said mixed gas 8.
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