Impedance control is one of the most effective control method for a manipulator in contact with its environment. The method, however, cannot control the end-effector impedance perfectly without an accurate model of the manipulator. Also, unexpected external disturbances are often applied to the manipulator, so that errors between a target impedance and a realized one may arise. The present paper proposes an impedance control of a manipulator in the presence of modeling error, and validity of the proposed method is verified through experiments using a direct-drive robot.