An illuminating device includes: a calibrating output unit for reading an output current command value corresponding to a specific brightness command value and for outputting the output current command value to a light source; a ratio calculating unit for calculating a ratio between an illuminance of illuminating light emitted from the light source and a prescribed illuminance value prescribed for the specific brightness command value; an illuminance calculating unit for calculating each illuminance when each output current command value matched with each brightness command value is outputted; and a calibrating unit for calibrating a relationship between each brightness command value and each output current command value in a conversion table such that each illuminance at the time when each output current command value matched with each brightness command value is outputted is set to each prescribed illuminance value prescribed for each of the brightness command values.