An insulated electric wire that has a superior water-stopping performance and has a configuration in which, even if water enters the insulated electric wire, the water is unlikely to stay inside the insulated electric wire, and a wire harness containing such an insulated electric wire. An insulated electric wire contains: an exposed portion in which an insulation covering is removed from the outer circumference of a conductor; in which the insulation covering covers the outer circumference of the conductor, and a water-stopping portion that is provided in an area extending from a part of the exposed portion to a part of the first covered portion, and in which gaps between the elemental wires constituting the conductor are filled with a water-stopping agent. A region of the second covered portion is a non-waterproof end that has a void between the elemental wires and/or between the conductor and the insulation covering.