In a sterilizer for sterilizing an object to be sterilized utilizing microwaves of a microwave oven for home use, an electrodeless discharge bulb, which seals a material such as mercury which discharges owing to receiving microwaves and emitting ultraviolet rays, is fixed in an inside of a container. An object to be sterilized is held in the container in a manner so that an objective face to be sterilized of the object faces an ultraviolet ray emitting face of the electrodeless discharge bulb. In such a state, the container is put into an inside of the microwave oven, and the microwaves are irradiated, so that the ultraviolet rays emitted from the electrodeless discharge bulb are irradiated to the objective face of the object for processing the serialization.