The toner supply roller 31 includes a roller shaft 31A made of metal, an inner spongy member 31B formed around the roller shaft 31A, and an outer spongy member 31C formed around the inner spongy member 31B. The inner spongy member 31B is formed of a closed cell foam material having electrically conductive properties. On the other hand, the outer spongy member 31C is formed of an open cell foam material having electrically conductive properties. Therefore, toner particles will not enter the cells formed in the inner spongy member 31B even after the toner supply roller 31 has been used for a long time.