An electrophotographic developer comprising a carrier and a magnetic toner, the magnetic toner containing a cycloolefin copolymer resin as a binder resin. The carrier is preferably one wherein the surface of core particles is coated with a resin coating agent, or a magnetic substance dispersion type resin carrier. When the saturation magnetization of carrier at an external magnetic field of 5 kOe is referred to as Sc, it is preferred that the saturation magnetization of magnetic toner at an external magnetic field of 5 kOe (St) satisfy the relationship: 0.10 Sc ≤ St ≤ 0.40 Sc. The electrophotographic developer excels in environmental characteristics, enables maintaining satisfactory image density at continuous copying of a multiplicity of sheets, is free from fogging and toner scattering problems, and can reduce the amount of toner consumed.