A vehicular lamp comprising: a front lens body extending in a predetermined direction; and a first optical system and a second optical system (30a, 30b) disposed adjacent to each other along the predetermined direction behind the front lens body, the first optical system includes: a first rear lens unit disposed behind the front lens body; and a first light source (42a-42d) which is disposed behind the first rear lens unit and emits light which is irradiated forward permeating the first rear lens unit and the front lens body in that order to form a first headlamp light distribution pattern, the second optical system includes: a second rear lens unit disposed behind the front lens body; and a second light source which is disposed behind the second rear lens unit and emits light which is irradiated forward permeating the second rear lens unit and the front lens body in that order to form a second headlamp light distribution pattern, wherein the light from the first light source which permeates the first rear lens unit and the front lens body forms a first light emitting region in the front lens body, and the light from the second light source which permeates the second rear lens unit and the front lens body forms a second light emitting region which at least partially overlaps with the first light emitting region in the front lens body, characterized in that a diffusion angle in horizontal direction of the light from the first light source which permeates the first rear lens unit and the front lens body is a first diffusion angle (θ3), a diffusion angle in horizontal direction of the light from the second light source which permeates the second rear lens unit and the front lens body is a second diffusion angle (θ4), wherein the second diffusion angle is larger than the first diffusion angle. a front lens body extending in a predetermined direction; and a first optical system and a second optical system (30a, 30b) disposed adjacent to each other along the predetermined direction behind the front lens body, the first optical system includes: a first rear lens unit disposed behind the front lens body; and a first light source (42a-42d) which is disposed behind the first rear lens unit and emits light which is irradiated forward permeating the first rear lens unit and the front lens body in that order to form a first headlamp light distribution pattern, a first rear lens unit disposed behind the front lens body; and a first light source (42a-42d) which is disposed behind the first rear lens unit and emits light which is irradiated forward permeating the first rear lens unit and the front lens body in that order to form a first headlamp light distribution pattern, the second optical system includes: a second rear lens unit disposed behind the front lens body; and a second light source which is disposed behind the second rear lens unit and emits light which is irradiated forward permeating the second rear lens unit and the front lens body in that order to form a second headlamp light distribution pattern, wherein a second rear lens unit disposed behind the front lens body; and a second light source which is disposed behind the second rear lens unit and emits light which is irradiated forward permeating the second rear lens unit and the front lens body in that order to form a second headlamp light distribution pattern, wherein the light from the first light source which permeates the first rear lens unit and the front lens body forms a first light emitting region in the front lens body, and the light from the second light source which permeates the second rear lens unit and the front lens body forms a second light emitting region which at least partially overlaps with the first light emitting region in the front lens body, characterized in that a diffusion angle in horizontal direction of the light from the first light source which permeates the first rear lens unit and the front lens body is a first diffusion angle (θ3), a diffusion angle in horizontal direction of the light from the second light source which permeates the second rear lens unit and the front lens body is a second diffusion angle (θ4), wherein the second diffusion angle is larger than the first diffusion angle.