Mixing-effective motions are both numerically and experimentally studied for a very viscous fluid around a rotating elliptic cylinder installed in a cylindrical vessel. A two-dimensional direct numerical simulation was conducted in an elliptic boundary-fitted curvilinear coordinate system rotating at the same angular velocity as the elliptic cylinder. Time-dependent streamlines and streaklines were observed with the aid of visualization technique. It is found that a mixing-effective (folding) motion actually occurs in the vicinity of the edges of the elliptic cylinder, and that such a motion may result from the unstableness of hyperbolic fixed points on an integrable two-dimensional heteroclinic orbit due to experimentally unavoidable three-dimensional disturbances.