Positively chargeable developer

A positively chargeable developer comprising at least positively chargeable toner particles each containing at least a binder resin and magnetic iron oxide, wherein:

• an inorganic fine powder is externally added to the positively chargeable toner particles,
• the inorganic fine powder comprises a magnesium oxide fine powder;
• the magnesium oxide fine powder comprises a crystal system having a peak at a Bragg angle (2θ±0.2 deg) of 42.9 deg in CuKα characteristic X-ray diffraction;
• and
• a half width of the X-ray diffraction peak at the Bragg angle (2θ±0.2 deg) of 42.9 deg is 0.40 deg or less,
• an unconfined yield strength (U5kPa) at a major consolidation stress of 5.0 kPa of the developer satisfies a relationship of 0.1 kPa≦U5kPa≦2.5 kPa;
• and
• an unconfined yield strength (U20kPa) at a major consolidation stress of 20.0 kPa of the developer satisfies a relationship of 2.5 kPa≦U20kPa≦5.5 kPa.