The present invention provides a pharmaceutical composition for prevention or treatment of osteoarthritis including cells or cell groups having a specific size or less, a kit for preparing a cell therapeutic agent, and a method for manufacturing a therapeutic agent for osteoarthritis. Mixed cells, which are selected to a specific size or less as an active ingredient of the present invention, of transformed mammalian cells with TGF-β and untransformed mammalian cells minimize aggregation between chondrocytes and have beneficial therapeutic effects. In addition, when administering the selected mixed cells having the specific size or less to a patient, patient compliance may be improved, and it is easy to manage quality in therapeutic agent manufacturing facilities or hospitals.
