The object of the invention is to achieve both the "oil-less fusing" and the elongation of lifetime of a developing unit. The first aspect of the invention is a toner being characterized in that the external additive coating ratio of toner particles of which mother particles have equivalent particle diameters larger than the mean particle diameter of the toner is set to be lower than a virtual reference curve in synchronous distribution of the equivalent particle diameters of synchronous external additive particles relative to the equivalent particle diameters of mother particles, wherein assuming that the external additive coating ratio of a toner particle of which a mother particle has an equivalent particle diameter equal to the mean particle diameter of the toner is a reference value, the virtual reference curve is obtained to satisfy that the external additive coating ratio is constant at the reference value. The second aspect of the invention is a toner being characterized in that the external additive coating ratio of toner particles of which mother particles have equivalent particle diameters smaller than the roughness of a developing roller is set to be higher than a virtual reference curve, wherein assuming that the external additive coating ratio of a toner particle of which a mother particle has an equivalent particle diameter equal to the roughness of the developing unit is a reference value, the virtual reference curve is obtained to satisfy that the external additive coating ratio is constant at the reference value. The third aspect of the invention is a toner being characterized in that the external additive coating ratio of toner particles of which mother particles have equivalent particle diameters larger than the roughness of a developing roller is set to be higher than a virtual reference curve, wherein assuming that the external additive coating ratio of a toner particle of which a mother particle has an equivalent particle diameter equal to the roughness of the developing unit is a reference value, the virtual reference curve is obtained to satisfy that the external additive coating ratio is constant at the reference value. The fourth aspect of the invention is a toner being characterized in that the external additive coating ratio of toner particles of which mother particles have equivalent particle diameters smaller than the mean particle diameter of the toner is set to be lower than a virtual reference curve, wherein assuming that the external additive coating ratio of a toner particle of which a mother particle has an equivalent particle diameter equal to the mean particle diameter of the toner is a reference value, the virtual reference curve is obtained to satisfy that the external additive coating ratio is constant at the reference value. The fifth aspect of the invention is an image forming apparatus comprising at least a latent image carrier on which an electrostatic latent image is formed, a developing unit for developing the electrostatic latent image on the latent image carrier with a toner, a transfer means for transferring the developed image on the latent image carrier, and a fusing means for fusing the transferred image, the image forming apparatus being characterized in that said toner is a toner of any one of the aforementioned aspects.