Development device, image forming apparatus, and development method

A development device comprising:

• an accommodation section that accommodates a developer;
• and
• a developer bearing member that carries the developer in the accommodation section, wherein
• the developer bearing member includes a magnetic member and a sleeve provided around the magnetic member rotatably around the magnetic member,
• the sleeve includes a metal substrate with a surface having projections and recesses and a plating layer covering the surface of the metal substrate,
• the plating layer contains chromium and cobalt,
• the developer contains a toner and the toner includes toner particles,
• the toner particles each include a toner mother particle and external additive particles attached to a surface of the toner mother particle,
• the toner mother particles contain a binder resin and a magnetic powder,
• the external additive particles include alumina particles with surfaces that are hydrophobized, and
• a number-average primary particle diameter of the alumina particles is more than 0.1 μm.