The present invention relates to a magnetic mono-component toner composition, and more particularly to a mono-component toner composition that comprises magnetic toner particle comprising a binder resin, a magnetic component, and a charge control agent; a hydrophobic treated silica having a specific surface area of 20 to 80 m.sup.2/g; a hydrophobic treated silica having a specific surface area of 130 to 230 m.sup.2/g; and a metal oxide fine powder. A magnetic mono-component toner composition of the present invention has such good flowability that it provides smooth toner supply even when the developing roller surface has been worn due to long time use, and it has such excellent uniform chargeability that it prevents image deterioration ("wave" patterns of toner may form on developing roller, that is, magnetic sleeve) by forming an uniform toner layer on the developing roller.