A headlight apparatus provided in a transportation vehicle, the headlight apparatus comprising: a light source unit including at least one light source and emitting a light in a forward direction of the transportation vehicle; a light source driving unit supplying a driving current to the at least one light source included in the light source unit; and a control unit receiving information about a travelling environment of the transportation vehicle and determining a driving condition of the light source unit by using the received information about the travelling environment, wherein the driving condition of the light source unit includes a driving current value corresponding to a brightness of the at least one light source included in the light source unit, and wherein the control unit is configured to: output a control signal to the light source driving unit so that the light source unit is driven according to the driving condition; wherein the information about the travelling environment of the transportation vehicle includes at least one of speed information corresponding to a travelling speed of the transportation vehicle and illuminance information corresponding to an ambient illuminance of the transportation vehicle, wherein the driving current value is changed in proportion to the travelling speed, or changed in inverse proportion to the ambient illuminance, wherein the control unit is further configured to maintain supplying a driving current value corresponding to a previous brightness during a predetermined time when decreasing the brightness of the at least one light source, or is further configured to gradually change the brightness of the at least one light source by using at least one driving current value existing between a driving current value corresponding to a previous brightness of the at least one light source and another driving current value corresponding to a present brightness of the at least one light source when a difference value between the previous brightness and the present brightness of the at least one light source exceeds a preset reference value. a light source unit including at least one light source and emitting a light in a forward direction of the transportation vehicle; a light source driving unit supplying a driving current to the at least one light source included in the light source unit; and a control unit receiving information about a travelling environment of the transportation vehicle and determining a driving condition of the light source unit by using the received information about the travelling environment, wherein the driving condition of the light source unit includes a driving current value corresponding to a brightness of the at least one light source included in the light source unit, and wherein the control unit is configured to: output a control signal to the light source driving unit so that the light source unit is driven according to the driving condition; wherein the information about the travelling environment of the transportation vehicle includes at least one of speed information corresponding to a travelling speed of the transportation vehicle and illuminance information corresponding to an ambient illuminance of the transportation vehicle, wherein the driving current value is changed in proportion to the travelling speed, or changed in inverse proportion to the ambient illuminance, wherein the control unit is further configured to maintain supplying a driving current value corresponding to a previous brightness during a predetermined time when decreasing the brightness of the at least one light source, or is further configured to gradually change the brightness of the at least one light source by using at least one driving current value existing between a driving current value corresponding to a previous brightness of the at least one light source and another driving current value corresponding to a present brightness of the at least one light source when a difference value between the previous brightness and the present brightness of the at least one light source exceeds a preset reference value. output a control signal to the light source driving unit so that the light source unit is driven according to the driving condition; wherein the information about the travelling environment of the transportation vehicle includes at least one of speed information corresponding to a travelling speed of the transportation vehicle and illuminance information corresponding to an ambient illuminance of the transportation vehicle, wherein the driving current value is changed in proportion to the travelling speed, or changed in inverse proportion to the ambient illuminance, wherein the control unit is further configured to maintain supplying a driving current value corresponding to a previous brightness during a predetermined time when decreasing the brightness of the at least one light source, or is further configured to gradually change the brightness of the at least one light source by using at least one driving current value existing between a driving current value corresponding to a previous brightness of the at least one light source and another driving current value corresponding to a present brightness of the at least one light source when a difference value between the previous brightness and the present brightness of the at least one light source exceeds a preset reference value.