Patent ID: 7907877

Claim:
A developing device, comprising: a toner bearing member that bears toner that has core particles and a particulate external additive externally added to the core particles, and that develops a latent image borne on an image bearing member using the toner, the toner bearing member being rotatable and having projecting sections arranged in a regular manner on a surface of the toner bearing member; and a regulation member that regulates an amount of toner borne on a surface of the toner bearing member by coming into contact with that surface at a contact section, the regulation member being arranged so that a longitudinal direction of the regulation member runs along an axial direction of the toner bearing member, and so that a leading edge of the regulation member in a lateral direction and a thickness direction faces an upstream side in a rotating direction of the toner bearing member, wherein in the case where a volume mean particle size of the toner is set to a toner particle size A, a volume mean particle size of the external additive is set to an external additive particle size B, a ten-point average roughness of the projecting sections is set to a protrusion roughness C, and a distance between the leading edge and the projecting sections in the case where the leading edge of the regulation member faces the projecting sections is set to a distance D, a relationship among sizes of the toner particle size A, the external additive particle size B, the protrusion roughness C, and the distance D is so that the protrusion roughness C<the external additive particle size B<the distance D<the toner particle size A.