Disclosed is a lighting device of a vehicle capable of achieving an enhancement in luminous efficacy. The disclosed lighting device includes a light source for generating light, a light guide including a light emitting portion formed with first patterns arranged in a longitudinal direction of the light emitting portion, to guide the light, the light emitting portion performing light emission using the light, and a light receiving portion to receive the light generated by the light source, and a back cover, on which the light guide is mounted. The back cover is formed with second patterns arranged in a longitudinal direction of the back cover at a portion of the back cover, on which the light receiving portion is mounted. The first patterns are formed to have a greater width with increasing distance from the light source. The second patterns are formed to have the same width.