A developing device according to an aspect of the invention includes: a housing; a developing roller comprising a roller main body having a circumferential surface, the developing roller being rotatably supported to the housing; and seal members respectively disposed to face both end portions of the circumferential surface of the roller main body with respect to a rotational axis direction thereof and to press contact with the roller main body. Each of the seal members comprises: a base material formed of an elastic element; and a sliding frictional member that is formed of fibers and contacts with the circumferential surface of the roller main body such that the roller main body frictionally slides on the sliding frictional member. Both edges of the circumferential surface of the roller main body with respect to the rotational axis direction thereof are brought into contact with the base materials.