To provide an ultraviolet irradiator having a function which supports a work for forming a test sample for determining the optimum ultraviolet irradiation time.

This ultraviolet irradiator for use in curing an ultraviolet curable resin is equipped with a light source of ultraviolet rays and a control part for controlling the luminous intensity and irradiation time of ultraviolet rays by controlling the bringhtness and drive time of a light source. The control part performs processing for inputting the irradiation energy of ultraviolet rays and the number of patterns corresponding to the product of the luminous intensity and the irradiation time, processing for forming a combination of the luminous intensity becoming the inputted irradiation energy of ultraviolet rays and the irradiation time by the inputted number of patterns and processing for controlling the brightness and drive time of the light source in order to successively perform the irradiation with ultraviolet rays by once according to the combination of the luminous intensity of the number of patterns and the irradiation time at each time when a command for performing the irradiation with ultraviolet reays is issued.