To efficiently separate paper and plastic by subjecting a mixture composed of paper and plastic to a moisture absorption treatment or absorption of an electrolytic soln. as a pretreatment, then subjecting this mixture to electrostatic separation.

The mixture composed of the paper 8 and the plastic 7 is subjected to the moisture absorption treatment such as spraying water drops or the soln. dissolved with the electrolyte under stirring the mixture as the pretreatment. The soln. of the electrolyte is otherwise absorbed therein. After the electrolyte is otherwise previously added to the mixture, the moisture absorption treatment is executed. An electrostatic field is thereafter formed by applying voltage between a fine wire electrode 1 and a roller electrode 2 to drop the mixture after the moisture absorption treatment onto the roller electrode 2. The plastic 7 having a high insulating characteristic, then, adheres to the roller electrode 2 and, therefore, the plastic is scraped off by a brush 3 and is captured into a collecting box 4. The paper and the like 8 which is lowered in the insulating characteristic and enhanced in the electrical conductivity by the moisture absorption fall as they are and are captured in a collecting box 5.