A rotary body sealing material device. The device prevents leakage of powder, by effectively sealing en end of a rotary body with a simple structure. An end seal which prevents toner leakage by contacting an outer circumference of a developing roller, has a contact portion made of a sealing material of yarns including porous hollow fibers. The seal, made of hollow fiber, exhibits reduced repulsive elasticity during compression, and high hermeticity is attained in the yarns by applying only a relatively light load to such an extent that deformation is not formed in a pressure-applying supporting plate and the to-be-pressed developing roller, thereby maintaining seal integrity.