Purification method propylene oxide.

A process for purifying propylene oxide, which comprises: subjecting a liquid reaction mixture containing propylene oxide obtained by reacting cumene hydroperoxide with propylene, and water, hydrocarbons and organic oxygen-containing compounds as impurities to extractive distillation using a hydrocarbon having 7 to 20 carbon atoms as an extractant, with an extractive distillation column, characterized by controlling a concentration of propylene glycol contained in the extractant supplied into the extractive distillation column is 20% by weight or less, washing the extractant with water.