The invention provides a cotton ball filling device, which comprises a rotatable roller. A chamber is formed in the roller; the chamber of the roller is connected with an air exhaust element capable of exhausting air from the inner part of the roller chamber; and multiple groups of adsorption through holes are formed in an outer surface of the roller, and are arranged at intervals along a rotationdirection of the roller. The cotton ball filing device further comprises cotton ball storage elements, wherein chambers capable of holding cotton balls are formed in the cotton ball storage elements;and openings in one ends of the cotton ball storage elements are connected with the outer surface of the roller, so that the cotton balls are adsorbed to the outer surface of the roller through the adsorption through holes. According to the cotton ball filing device provided by the invention, the work efficiency of a cotton ball filling process can be improved, and the quality of the cotton ballsis ensured.