A light irradiation apparatus comprising: an elongated body; a light emitting diode chip that is closely fixed to a tip portion of the elongated body and that emits ultraviolet light, the LED chip being comprised of aluminium gallium nitride (AlGaN), an anode electrode, and a cathode electrode; and a cover unit that is formed of a material that covers the LED chip so as to protect the LED chip and allows the ultraviolet light emitted by the LED chip to pass therethrough, wherein the elongated body has: a conductive unit that extends in a longitudinal direction of the elongated body, that is connected to the anode and the cathode electrodes, and that passes electric current for allowing the LED chip to emit light; and an insulation unit that covers the conductive unit so as to ensure electrical insulation of the conductive unit, wherein the insulation unit is a resin material, wherein the light irradiation apparatus is used for disinfection treatment of an object by allowing the LED chip to emit light while the elongated body is inserted into a narrow part, and wherein the LED chip has a size of 0.1 mm to 1 mm square, the elongated body has a diameter of 1.5 mm to 3 mm and a flexibility that allows for elastic restoration, thereby having a rigidity that allows the elongated body to pass through the entrance to the inside of the pipe, and a plasticity that allows the elongated body to bend to a curvature radius 10 times the diameter thereof without buckling, and the cover unit is formed of an amorphous fluorine-based resin, wherein the cover unit covers the LED chip, and forms an outer side of the apparatus. an elongated body; a light emitting diode chip that is closely fixed to a tip portion of the elongated body and that emits ultraviolet light, the LED chip being comprised of aluminium gallium nitride (AlGaN), an anode electrode, and a cathode electrode; and a cover unit that is formed of a material that covers the LED chip so as to protect the LED chip and allows the ultraviolet light emitted by the LED chip to pass therethrough, wherein the elongated body has: a conductive unit that extends in a longitudinal direction of the elongated body, that is connected to the anode and the cathode electrodes, and that passes electric current for allowing the LED chip to emit light; and an insulation unit that covers the conductive unit so as to ensure electrical insulation of the conductive unit, wherein the insulation unit is a resin material, wherein the light irradiation apparatus is used for disinfection treatment of an object by allowing the LED chip to emit light while the elongated body is inserted into a narrow part, and wherein the LED chip has a size of 0.1 mm to 1 mm square, the elongated body has a diameter of 1.5 mm to 3 mm and a flexibility that allows for elastic restoration, thereby having a rigidity that allows the elongated body to pass through the entrance to the inside of the pipe, and a plasticity that allows the elongated body to bend to a curvature radius 10 times the diameter thereof without buckling, and the cover unit is formed of an amorphous fluorine-based resin, wherein the cover unit covers the LED chip, and forms an outer side of the apparatus. a conductive unit that extends in a longitudinal direction of the elongated body, that is connected to the anode and the cathode electrodes, and that passes electric current for allowing the LED chip to emit light; and an insulation unit that covers the conductive unit so as to ensure electrical insulation of the conductive unit, wherein the insulation unit is a resin material, wherein the light irradiation apparatus is used for disinfection treatment of an object by allowing the LED chip to emit light while the elongated body is inserted into a narrow part, and wherein the LED chip has a size of 0.1 mm to 1 mm square, the elongated body has a diameter of 1.5 mm to 3 mm and a flexibility that allows for elastic restoration, thereby having a rigidity that allows the elongated body to pass through the entrance to the inside of the pipe, and a plasticity that allows the elongated body to bend to a curvature radius 10 times the diameter thereof without buckling, and the cover unit is formed of an amorphous fluorine-based resin, wherein the cover unit covers the LED chip, and forms an outer side of the apparatus.