The invention relates to a motor vehicle door lock equipped with a locking mechanism, an actuation lever unit that acts on the locking mechanism and includes a release lever, and a catch lever. The illuminating unit is aligned as an arrowhead shape in such a manner when the vehicle signal light is switched on, the illuminating unit is automatically switched on in order to signify the further motion of the vehicle. With this structure, voltage applied between the source and the gate of the transistor can be corrected in anticipation of variations in threshold voltage, so that the current supplied to the light-emitting element can be corrected. The sensor rod has one end that rotatably engages the agitating member and the other end to which a detector is attached.