A vehicle-purpose lighting tool is featured by comprising: a light-conducting member having a front light-emitting plane, a rear plane having a concave/convex shape, and a side edge plane; and a light source arranged at a position opposite to the side edge plane; in which within external light which is entered via the front light-emitting plane into the light-conducting member, a portion of the external light which is directly traveled to the side edge plane is totally reflected on a boundary plane of the side edge plane portion; a plurality of reflecting portions are formed on the rear plane and are coupled to each other via a coupling portion in such a direction that the reflecting portions are separated apart from the side edge plane side; and distances between the plurality of reflecting portions and the front light-emitting plane are changed in a discontinuous manner along the separating direction.