A steering light device is mounted on left or right sides of a motorcycle having an imaginary middle vertical plane extending horizontally in a front-rear direction. The steering light device includes a light unit and a lens unit. The light unit includes at least one inclined elongate auxiliary light descending inwardly toward the imaginary middle vertical plane. The lens unit includes at least one auxiliary lens cooperating respectively with the main and auxiliary lights to project light for compensating light intensity of a dark area in a road surface located in front of the motorcycle when steering the motorcycle to a corresponding one of the left or right.