It is to provide a toner which can form an image of high image quality exhibiting high resolution wherein a final visible image exhibits high image density and high thin-line reproducibility even in long-term use. In a toner incorporating at least a colored particle containing a binder resin composed of a polyester resin and a colorant, and external additive particles, the toner has a degree of average circularity of 0.950-0.990, a volume based median diameter of 4.5-8.0 .mu.m, a volume based particle diameter dispersibility (CV.sub.VOL value) of 15-25; a metal selected from titanium, germanium, and aluminum is incorporated at a ratio of 10-1500 ppm; the above external additive particles is composed of a composite oxide incorporating a silicon atom and at least either of a titanium atom and an aluminum atom; and the existence ratio of silicon atoms in the surface thereof is higher than the existence ratio of silicon atoms in the entire part thereof.