An image forming apparatus comprising a developing device (3a-3d) and an image carrier (1a to 1d), the developing device (3a-3d) comprising: a developing container for accommodating a two-component developer containing a magnetic carrier and a toner; a toner carrier having some of an external peripheral surface exposed through an opening in the developing container, whereby the toner carrier is arranged so as to face the image carrier (la told), the toner carrier supplying toner to the image carrier (la to 1d) a developer carrier which is placed facing the toner carrier, the developer carrier rotating so that a surface facing the toner carrier moves in the opposite direction of the toner carrier, and a toner layer being formed on the toner carrier using a magnetic brush comprising a two-component developer supported on a surface of the developer carrier; and a regulating member for regulating the amount of developer carried on the developer carrier;and an air outflow channel for communicating an airflow outlet formed in a top end of the developing container facing the toner carrier with the interior of a duct placed above the developing container at a position higher than the toner carrier; the airflow outlet being provided to a position, relative to the rotational direction of the toner carrier, that is farther downstream than a vertical line passing through the rotational axis center of the toner carrier, characterized in that the toner carrier is arranged to supply toner to the image carrier (1a to 1d) while rotating so that the surface of toner carrier facing the image carrier (1a to 1d) moves upward; the air outflow channel extends obliquely upward downstream in the rotational direction of the toner carrier from the airflow outlet to an airflow inlet of the duct communicating with the outflow channel, and the airflow outlet is provided to a position, relative to the rotational direction of the toner carrier, that is farther upstream than a position distanced 90° upstream from the facing portion of the developer carrier and the toner carrier. a developing container for accommodating a two-component developer containing a magnetic carrier and a toner; a toner carrier having some of an external peripheral surface exposed through an opening in the developing container, whereby the toner carrier is arranged so as to face the image carrier (la told), the toner carrier supplying toner to the image carrier (la to 1d) a developer carrier which is placed facing the toner carrier, the developer carrier rotating so that a surface facing the toner carrier moves in the opposite direction of the toner carrier, and a toner layer being formed on the toner carrier using a magnetic brush comprising a two-component developer supported on a surface of the developer carrier; and a regulating member for regulating the amount of developer carried on the developer carrier;and an air outflow channel for communicating an airflow outlet formed in a top end of the developing container facing the toner carrier with the interior of a duct placed above the developing container at a position higher than the toner carrier; the airflow outlet being provided to a position, relative to the rotational direction of the toner carrier, that is farther downstream than a vertical line passing through the rotational axis center of the toner carrier, characterized in that the toner carrier is arranged to supply toner to the image carrier (1a to 1d) while rotating so that the surface of toner carrier facing the image carrier (1a to 1d) moves upward; the air outflow channel extends obliquely upward downstream in the rotational direction of the toner carrier from the airflow outlet to an airflow inlet of the duct communicating with the outflow channel, and the airflow outlet is provided to a position, relative to the rotational direction of the toner carrier, that is farther upstream than a position distanced 90° upstream from the facing portion of the developer carrier and the toner carrier.