The 1st development agent transportation path which

摘要

PROBLEM TO BE SOLVED: To prevent image density irregularity caused by toner concentration irregularity and uneven distribution of a developer in a developing device using a two-component developer.SOLUTION: The developing device includes: first and second developer conveying passages for circulating and conveying a two-component developer; a first conveying member, which is rotatably disposed inside the first developer conveying passage and has a spiral blade with a spiral pitch gradually decreasing from an upstream side to a downstream side in a developer conveying direction; a second conveying member, which is disposed inside the second developer conveying passage; a developing roller, which supplies the developer in the first developer conveying passage to a photoreceptor drum; a developer recovering passage for guiding the developer remaining on the surface of the developing roller into a direction apart from the first developer conveying passage; a third developer conveying passage for conveying the developer guided by the developer recovering passage; a third conveying member, which is disposed inside the third developer conveying passage; a third communicating passage for guiding the developer in the third developer conveying passage into the second developer conveying passage; and a developer surface level controlling window, which has a predetermined height and guides an excess developer exceeding the height of the window from the first developer conveying passage into the developer recovering passage.