A lamp device (1LF, 3LF, 4LF) adapted to be mounted on a vehicle, comprising: a plurality of light sources (141, 341); a first sensor (151, 351) configured to sense external information of the vehicle; a lamp housing (143, 343, 443) that houses the light sources; a first sensor housing (152, 352, 452) that houses the first sensor; and a first supporting member (17, 37, 47) that supports the lamp housing and the first sensor housing, wherein the lamp housing and the first sensor housing are arranged in a direction corresponding to a left-right direction of the vehicle when viewed from a direction corresponding to a front-rear direction of the vehicle; and wherein a maximum dimension (UD1, UD5, UD8) of the lamp housing in a direction corresponding to an up-down direction of the vehicle is smaller than a maximum dimension (UD2, UD6, UD9) of the first sensor housing in the same direction, wherein the lamp device further comprises: a second sensor (161, 361) configured to sense external information of the vehicle in a manner that is different from the first sensor (151, 351); and a second sensor housing (162, 362, 462) that houses the second sensor, wherein the lamp housing is located between the first sensor housing and the second sensor housing; wherein an upper end (143a, 343a) of the lamp housing is located below an upper end (152a, 352a) of the first sensor housing and an upper end (162a, 362a) of the second sensor housing; and wherein a lower end (143b, 343b) of the lamp housing is located above a lower end (152b, 352b) of the first sensor housing and a lower end (162b, 362b) of the second sensor housing. a plurality of light sources (141, 341); a first sensor (151, 351) configured to sense external information of the vehicle; a lamp housing (143, 343, 443) that houses the light sources; a first sensor housing (152, 352, 452) that houses the first sensor; and a first supporting member (17, 37, 47) that supports the lamp housing and the first sensor housing, wherein the lamp housing and the first sensor housing are arranged in a direction corresponding to a left-right direction of the vehicle when viewed from a direction corresponding to a front-rear direction of the vehicle; and wherein a maximum dimension (UD1, UD5, UD8) of the lamp housing in a direction corresponding to an up-down direction of the vehicle is smaller than a maximum dimension (UD2, UD6, UD9) of the first sensor housing in the same direction, wherein the lamp device further comprises: a second sensor (161, 361) configured to sense external information of the vehicle in a manner that is different from the first sensor (151, 351); and a second sensor housing (162, 362, 462) that houses the second sensor, wherein the lamp housing is located between the first sensor housing and the second sensor housing; wherein an upper end (143a, 343a) of the lamp housing is located below an upper end (152a, 352a) of the first sensor housing and an upper end (162a, 362a) of the second sensor housing; and wherein a lower end (143b, 343b) of the lamp housing is located above a lower end (152b, 352b) of the first sensor housing and a lower end (162b, 362b) of the second sensor housing. a second sensor (161, 361) configured to sense external information of the vehicle in a manner that is different from the first sensor (151, 351); and a second sensor housing (162, 362, 462) that houses the second sensor, wherein the lamp housing is located between the first sensor housing and the second sensor housing; wherein an upper end (143a, 343a) of the lamp housing is located below an upper end (152a, 352a) of the first sensor housing and an upper end (162a, 362a) of the second sensor housing; and wherein a lower end (143b, 343b) of the lamp housing is located above a lower end (152b, 352b) of the first sensor housing and a lower end (162b, 362b) of the second sensor housing.