Optical unit and vehicular lamp

[TASK] To provide art for forming a light distribution pattern that has a clear vertical cut-off line with the use of a parabolic vehicular lamp. [MEANS OF SOLVING THE PROBLEM] A vehicular lamp is for froming a light distribution pattern that has a vertical cut-off line. The vehicular lamp has a light-emitting element 34a that has a genrally rectangular light-emitting surface 34af and a parabola optical system reflector 32b that reflects light from the light-emitting element 34a to the front of the lamp, and is configured to form the vertical cut-off line with the use of a long side 34af1 of the light-emitting surface 34af.