A protecting agent-supplying device which supplies, to an image bearing member, an image bearing member-protecting agent for protecting the image bearing member, wherein the image bearing member-protecting agent contains at least a fatty acid zinc salt and boron nitride, and wherein the protecting agent-supplying device supplies the image bearing member-protecting agent to the image bearing member so that the amount of zinc (Zn) present on a surface of the image bearing member satisfies the relation 0.4≦Zn≦2.5 (Atomic %) and the amount of boron (B) present on the surface of the image bearing member satisfies the relation 0.2≦B≦30.2 (Atomic %).