To make it possible to make the amount of the fine powder toners included in the toner existing in an image forming device less than that in a current state by disposing a means for classifying toner particles having a high electrostatic charge quantity by executing classification using electrical force.

The classification is executed by moving the toners 7 to a certain specified direction from the toners 7 housed in a toner container 11 and applying an electric field E in place of wind force in a direction perpendicular to the moving direction thereof, thereby moving the toners (microtoners) of the extremely high charge included in the toners 7 in the electric field direction. In such a case, the classification may be executed more effectively by agitating an agitating rod 13 at a ratio of about one revolution/second before allowing a developer to fall by gravity from the toner container 11. The reason thereof lies in that the triboelectrostatic charge between the toner particles with each other or between the toner particles and the agitating rod 13 is generated and the fine powder toners are more strongly electrostatically charged.