A vehicular lamp unit, comprising: a substrate; a light source comprising a first light-emitting element (L4, L5) and a second light-emitting element (L6-L9) disposed on the substrate; and an optical element having the light source attached thereto, wherein the substrate is long in a first direction, wherein the optical element is configured to radiate emitted light of the first and second light-emitting elements (L4-L9) toward a front of the vehicular lamp unit, with a desired light distribution, wherein first and second reference holes (24, 25) serving as positioning references for the optical element are provided in a part of the substrate, wherein the first and second light-emitting elements (L4-L9) are arranged in the first direction, wherein the first light-emitting element (L4, L5) is configured to illuminate an area (A4, A5) having high light intensity of the light distribution, and wherein the second light-emitting element (L6-L9) is configured to illuminate an area (A6-A9) having low light intensity of the light distribution, characterized in that first and second positioning pins (34, 35) of the optical element are inserted through the first and second reference holes (24, 25), there is no play in the first direction and a second direction perpendicular to the first direction between the first reference hole and the first positioning pin, the second reference hole is a hole that is long in the first direction, there is no play in the second direction between the second reference hole and the second positioning pin, and the first light-emitting element (L4, L5) is mounted at a position closer to the first reference hole in the first direction than the second light-emitting element (L6-L9). a substrate; a light source comprising a first light-emitting element (L4, L5) and a second light-emitting element (L6-L9) disposed on the substrate; and an optical element having the light source attached thereto, wherein the substrate is long in a first direction, wherein the optical element is configured to radiate emitted light of the first and second light-emitting elements (L4-L9) toward a front of the vehicular lamp unit, with a desired light distribution, wherein first and second reference holes (24, 25) serving as positioning references for the optical element are provided in a part of the substrate, wherein the first and second light-emitting elements (L4-L9) are arranged in the first direction, wherein the first light-emitting element (L4, L5) is configured to illuminate an area (A4, A5) having high light intensity of the light distribution, and wherein the second light-emitting element (L6-L9) is configured to illuminate an area (A6-A9) having low light intensity of the light distribution, characterized in that first and second positioning pins (34, 35) of the optical element are inserted through the first and second reference holes (24, 25), there is no play in the first direction and a second direction perpendicular to the first direction between the first reference hole and the first positioning pin, the second reference hole is a hole that is long in the first direction, there is no play in the second direction between the second reference hole and the second positioning pin, and the first light-emitting element (L4, L5) is mounted at a position closer to the first reference hole in the first direction than the second light-emitting element (L6-L9).