The invention discloses a processing box for a laser printer, which comprises a photosensitive drum for forming an electrostatic latent image, a development roller for conveying a development agent to the surface of the photosensitive drum, and a powder outlet knife for adjusting the thickness of a carbon powder layer on the surface of the development roller. The sliding friction coefficient of the mutually contacted parts of the development roller and the powder outlet knife is kept at 0.1 to 2.0. The processing box can effectively avoid flying and deposition of carbon powder due to insufficient electric quantity or over low electric quantity and avoid environmental pollution or avoid affecting the printing quality.