A structure for installing a wire harness within a vehicle door, wherein a wire harness is placed obliquely alongside the vehicle door and swingingly supported at a vertical position to avoid the stress of the wire harness to be caused when the door is opened or closed. The swinging portion of the wire harness is passed through the swinging portion of a protector. One end of the swinging portion of the wire harness is rotatably connected to a sliding portion of the protector and the other end of the swinging portion is rotatably supported at the vehicle door side. The position at which the swinging portion of the wire harness is supported is set to be the center of a range in which the protector slides. A case fitted into a door panel or formed integrally with a door trim and a cover hinged to the case can be employed to enclose the protector and the swinging portion of the wire harness fixed to a clamp holding portion with use of a clamp.