The present invention relates to a pharmaceutical composition for treating and/or preventing arthritis, which comprising, as an active ingredient, a gene delivery vehicle into which an IK factor or a fragment thereof, or a nucleic acid encoding thereof is inserted. IK factor or the fragment thereof, and the nucleic acid encoding thereof, which are the active ingredient of the pharmaceutical composition according to the present invention, are derived from an organism and therefore, show no side effects in administered into a subject for a long time. Accordingly, they ensures safety and are expected to effectively treat arthritis by being involved in the upstream mechanism for suppressing arthritis.