PURPOSE: To separate and to purify a polyphenol useful as a raw material for polyurethane, etc. in high purity in high yield, by dissolving a polyphenol obtained by a specified reaction in a specific mixed solvent, washing it with water, distilling away the solvent.

CONSTITUTION: An aldehyde shown by the formula I (Y is CH3, OCH3, Cl, Br, I; n is 0W2) is reacted with pentaerythritol in the presence of an acidic catalyst such as p-toluenesulfonic acid, etc. in a solvent comprising an aromatic hydrocarbon such as benzene, etc. as a main component to give a polyphenol shown by the formula II, and the solvent is distilled away from the reaction solution. The polyphenol is dissolved in a mixed solvent consisting of (A) 30W90wt% cyclohexane and (B) 70W10wt% methyl ethyl ketone and/or methyl isobutyl ketone, washed with water, the mixed solvent is distilled away, and the polyphenol shown by the formula II is separated and purified as a solid.