Developing Device and Image Forming Apparatus

An image forming apparatus provided with a developing device supplying a two-component developer to a developing roller, while causing the developer to circulate in a circulating passage including a first conveying passage and a second conveying passage arranged in parallel to each other, and while ejecting a part of the developer to outside via an ejection passage formed as an extension of the first conveying passage on a downstream side in a developer conveying direction, the developing roller being provided along the first conveying passage, the developing device including:

• a first communication path provided as a branch of the first conveying passage on the downstream side in the developer conveying direction and configured to allow the first conveying passage to communicate with the second conveying passage;
• a first conveying part configured to convey the developer in the first conveying passage toward the first communication path;
• and
• an entrance allowance unit configured to allow the developer to enter the ejection passage from the first conveying passage depending on a pressure of the developer in the first conveying passage,
• the first conveying part including a main conveying part and a sub-conveying part, the main conveying part being provided to cover at least a region corresponding to the developing roller, and the sub-conveying part, provided downstream of the main conveying part in the developer conveying direction, conveying a smaller amount of developer per unit time than the main conveying part.