Developing device with structure to release inner pressure

A developing device comprising:

• a developing roller;
• a developer conveying unit comprising a developing chamber provided with the developing roller and extending in a longitudinal direction of the developing roller, a stirring chamber arranged in parallel to the developing chamber, and a barrier wall having a first communication port and a second communication port, at respective ends in the longitudinal direction, to connect the developing chamber with the stirring chamber;
• a first conveying member located in the developing chamber to convey a developer from the second communication port in a first direction;
• a second conveying member located in the stirring chamber to convey a developer from the first communication port in a second direction opposite to the first direction;
• a developer discharge unit extending from the developing chamber in the first direction and including a developer discharge port to discharge excess developer;
• and
• an air discharge port to house a filter to filter a developer, the air discharge port being provided between the first communication port and the developer discharge unit to discharge air in the developer conveying unit.