A tractor comprising a headlight device having a bonnet, comprising: a pair of high-beam units; and a pair of low-beam units each including a lamp, a housing and a lens, wherein each high-beam unit comprises: a high-beam lamp; a high-beam lamp housing supporting the high-beam lamp; and a high-beam lamp lens covering the high-beam lamp, and wherein each of the high-beam lamp lenses are formed from a front surface to a side surface of the bonnet, wherein the high-beam lamp lens are formed so as to be projected from the side surface of the bonnet, characterized in that the high-beam units and the low-beam units are arranged respectively at an illumination part in a front surface of the bonnet having upper and lower two stages, and wherein the high-beam unit further comprises: a reflector reflecting light of the high-beam lamp; and an inner casing covering the reflector, and wherein the inner casing is projected from the side surface of the bonnet and formed along an inner surface of the high-beam lamp lens, wherein the inner casing is separated from the inner surface of the high beam lamp lens, so that light of the high-beam lamp passes between the outer surface of the inner casing and the inner surface of the high-beam lamp lens and illuminates a side surface of the bonnet. a pair of high-beam units; and a pair of low-beam units each including a lamp, a housing and a lens, wherein each high-beam unit comprises: a high-beam lamp; a high-beam lamp housing supporting the high-beam lamp; and a high-beam lamp lens covering the high-beam lamp, and wherein each of the high-beam lamp lenses are formed from a front surface to a side surface of the bonnet, wherein the high-beam lamp lens are formed so as to be projected from the side surface of the bonnet, characterized in that the high-beam units and the low-beam units are arranged respectively at an illumination part in a front surface of the bonnet having upper and lower two stages, and wherein the high-beam unit further comprises: a reflector reflecting light of the high-beam lamp; and an inner casing covering the reflector, and wherein the inner casing is projected from the side surface of the bonnet and formed along an inner surface of the high-beam lamp lens, wherein the inner casing is separated from the inner surface of the high beam lamp lens, so that light of the high-beam lamp passes between the outer surface of the inner casing and the inner surface of the high-beam lamp lens and illuminates a side surface of the bonnet. a high-beam lamp; a high-beam lamp housing supporting the high-beam lamp; and a high-beam lamp lens covering the high-beam lamp, and wherein each of the high-beam lamp lenses are formed from a front surface to a side surface of the bonnet, wherein the high-beam lamp lens are formed so as to be projected from the side surface of the bonnet, characterized in that the high-beam units and the low-beam units are arranged respectively at an illumination part in a front surface of the bonnet having upper and lower two stages, and wherein the high-beam unit further comprises: a reflector reflecting light of the high-beam lamp; and an inner casing covering the reflector, and wherein the inner casing is projected from the side surface of the bonnet and formed along an inner surface of the high-beam lamp lens, wherein the inner casing is separated from the inner surface of the high beam lamp lens, so that light of the high-beam lamp passes between the outer surface of the inner casing and the inner surface of the high-beam lamp lens and illuminates a side surface of the bonnet. a reflector reflecting light of the high-beam lamp; and an inner casing covering the reflector, and wherein the inner casing is projected from the side surface of the bonnet and formed along an inner surface of the high-beam lamp lens, wherein the inner casing is separated from the inner surface of the high beam lamp lens, so that light of the high-beam lamp passes between the outer surface of the inner casing and the inner surface of the high-beam lamp lens and illuminates a side surface of the bonnet.