To utilize minus ions for lives to use the effects, because it is desired that the minus ions can be utilized without limiting shapes, weights, materials, uses and places to be used, because the minus ions are rapidly increased in the modern life environments due to the generation of large quantities of electromagnetic waves from various electric and electronic equipment such as televisions, cell phones, microwave ovens, refrigerators, and air conditioners, and because all of exhaust gases from factories and automobiles are harmful plus ions which oxidize body fluids to weaken the resistance of the bodies, thereby causing the various bad conditions of the bodies.

A minus ion-generating natural mineral is adhered to mulberry leaves which are feed for silkworms of natural organism, and then given as the feed to the silkworms. The silk fibers taken out from cocoons which are spun from the silkworms and are the raw materials of the natural silk fibers generate minus ions, and it can be expected to effectively use the minus ions.