To provide a method for preventing a polymer from adhering to the inner wall surface of a reaction vessel and so on, when forming the particles of a polymer having a polar group in an aqueous solution and separating them, without using a large-scale apparatus and also needing particularly a periodic maintenance.

The method for preventing a polymer from adhering to the inner wall surface of a reaction vessel at the time of forming particles of a polymer having a polar group in an aqueous solution in a reaction vessel, is characterized by using an optical semiconductor catalyst material on the inner wall surface of the above reaction vessel and also by carrying out the formation of the above polymer particles at a state that the above optical semiconductor catalyst has been excited.