An image forming apparatus, a process cartridge, and a developing unit includes a developer carrying member to carry developer, first and second rotary members arranged in parallel to each other and configured to rotate to agitate and convey the developer, and an enclosure having an inside space to contain the developer, the inside space being divided by a partition with communication openings formed therein at opposite ends thereof into a first chamber configured to maintain the developer above a first level and to hold the first rotary member therein which supplies the developer to the developer carrying member while agitating and conveying the developer, and a second chamber configured to communicate with the first chamber through the communication openings, to maintain the developer at a second level lower than the first level, and to hold the second rotary member therein which circulates the developer with the first chamber through the communication openings.