Developing device capable of suppressing the passing of a relatively large amount of developer and image forming apparatus therewith

A developing device comprising:

• a housing that includes a container portion containing developer and that has a developing opening;
• a developer holding device that holds the developer in the container portion of the housing and that is rotated so as to pass the developing opening;
• and
• a directing device,
• wherein the developing device has a through portion disposed at a portion of the housing including a downstream edge portion at a downstream portion of the developing opening in a direction in which the developer holding device is rotated,
• wherein the through portion has an inlet, an outlet, and a passage that connects the inlet and the outlet to each other so as to allow part of an airflow generated by rotation of the developer holding device to be introduced thereinto and flow therethrough,
• wherein the directing device extends from a portion of the housing opposite to the developing opening with the inlet of the through portion interposed therebetween toward the developer holding device so as to direct the part of the airflow toward the inlet, and
• wherein, in an axial direction of the developer holding device, an opening area of a portion of the inlet of the through portion disposed in a central region is larger than a total of opening areas of portions of the inlet of the through portion disposed in end regions,
• wherein a height of the opening area of the portion of the inlet of the through portion disposed in the central region is larger than a height of the opening areas of the portions of the inlet of the through portion disposed in the end regions.