A backlight unit for blind spot warning lighting for a vehicle comprising: a printed circuit board, PCB, mounted to a light-emitting diode, LED; a bottom case having the PCB embedded on a lower portion thereof, and having an opened front surface; and a top case comprising a front plate covering the opened front surface of the bottom case, the top case further comprising: a guide protruding backward from a rear surface of the front plate to guide light from the LED to the front plate, characterised in that the guide comprises: a guide part comprising a first side portion and a second side portion for guiding the light from the LED; a light incident part disposed upward from the LED and positioned at a height lower than a height of a lower end of the first side portion and the second side portion; and a pair of inclined parts, each of which connected from each of both ends of the light incident part up to both lower ends of the first side portion and the second side portion respectively, whereby the backlight unit includes an adhesive tape bonded to the front surface of the front plate of the top case, the adhesive tape having a plurality of transparent regions on which an image is displayed, wherein all of the transparent regions of the adhesive tape is positioned at a location higher than the inclined part. a printed circuit board, PCB, mounted to a light-emitting diode, LED; a bottom case having the PCB embedded on a lower portion thereof, and having an opened front surface; and a top case comprising a front plate covering the opened front surface of the bottom case, the top case further comprising: a guide protruding backward from a rear surface of the front plate to guide light from the LED to the front plate, characterised in that the guide comprises: a guide part comprising a first side portion and a second side portion for guiding the light from the LED; a light incident part disposed upward from the LED and positioned at a height lower than a height of a lower end of the first side portion and the second side portion; and a pair of inclined parts, each of which connected from each of both ends of the light incident part up to both lower ends of the first side portion and the second side portion respectively, whereby the backlight unit includes an adhesive tape bonded to the front surface of the front plate of the top case, the adhesive tape having a plurality of transparent regions on which an image is displayed, wherein all of the transparent regions of the adhesive tape is positioned at a location higher than the inclined part. a guide protruding backward from a rear surface of the front plate to guide light from the LED to the front plate, characterised in that the guide comprises: a guide part comprising a first side portion and a second side portion for guiding the light from the LED; a light incident part disposed upward from the LED and positioned at a height lower than a height of a lower end of the first side portion and the second side portion; and a pair of inclined parts, each of which connected from each of both ends of the light incident part up to both lower ends of the first side portion and the second side portion respectively, whereby the backlight unit includes an adhesive tape bonded to the front surface of the front plate of the top case, the adhesive tape having a plurality of transparent regions on which an image is displayed, wherein all of the transparent regions of the adhesive tape is positioned at a location higher than the inclined part. a guide part comprising a first side portion and a second side portion for guiding the light from the LED; a light incident part disposed upward from the LED and positioned at a height lower than a height of a lower end of the first side portion and the second side portion; and a pair of inclined parts, each of which connected from each of both ends of the light incident part up to both lower ends of the first side portion and the second side portion respectively, whereby the backlight unit includes an adhesive tape bonded to the front surface of the front plate of the top case, the adhesive tape having a plurality of transparent regions on which an image is displayed, wherein all of the transparent regions of the adhesive tape is positioned at a location higher than the inclined part.