A main path in an optical waveguide with a light-emitting element has two sides faced to each other: one side has a plurality of branched points and the other side does not have any branched points. A width W of the main path becomes narrower as the main path moves away from a light-emitting element. An angle α formed by the main path and a light guiding direction in each branched point of each branched path is 0.1° to 2.0°. An angle θ formed by the other side without branched points and the light guiding direction of the main path is 0.3° to 1.7°.