An ultraviolet light sterilizer includes: a deep ultraviolet light source comprising one or more deep ultraviolet light emitting diode and irradiating a deep ultraviolet ray toward a work and a controller controlling (1) an irradiation time t (unit: second) defined as a time for which the deep ultraviolet ray is irradiated to the work, (2) a distance d (unit: cm) between the work and the deep ultraviolet light source, or (3) an emission power P (unit: mW) of the deep ultraviolet light source, or combination thereof, such that an integral irradiance I (unit: mJ/cm2) of the deep ultraviolet ray irradiated to the work during the irradiation time reaches a predetermined value I0.
