To exhibit a conventional wiping cleaning effect and an external leakage preventing effect of powder (toner) while attaining marked cost reduction without impairing performance by developing a seal material piece made of ultrafine fiber nonwoven fabric as a seal material piece of a powder seal piece in place of a conventional extremely-expensive seal material piece made of polytetrafluorethylene.

The seal material piece 8 sticking to the inner surface of a bearing part recess 6 of the rotating shaft 1 for a toner case or the like to seal a powder leakage, is formed of: a powder seal piece A formed by using a paper-like ultrafine fiber nonwoven fabric obtained by forming synthetic fiber with ultrafine dividable property in the longitudinal direction of fiber, into ultrafine fiber in nano units by an inclined beating method and entangling the fibers with one another by a water jet method which is a nonwoven fabric processing method; and the powder real piece A which is provided with parallel projections 10 formed in the longitudinal direction of the nonwoven fabric surface, in conformity to the longitudinal direction of the surface of the seal material piece 8.