To provide a development device for an image forming apparatus, which hinders an amount of developer sticking to a development sleeve from varying with temperature/humidity of the environment, thereby making it possible to form an image of satisfactory image quality.

The development sleeve, as a developer carrier, rotatably supported is disposed in contact with an image carrier 11. When low humidity is detected by an environmental sensor 30, an amount of electrified developer increases with the result that an abnormal increase (runaway) in the amount of developer sticking to the development sleeve may occur. To counter this, the contact area of a discharge member 28 with the development sleeve is increased or a period for which the member 28 is in contact with the sleeve is increased to decrease the amount of electrified developer. Conversely when high humidity is detected by the environmental sensor, the contact area of the discharge member with the development sleeve is decreased or the rotating speed of the development sleeve 22 is increased to decrease a period for which the discharge member 28 is in contact with the development sleeve 22, thereby imparting a sufficient amount of electrification to the developer.