To appropriately separate a developer returned into a device body from a surface of a developer carrier between magnetic poles having the same polarity next to each other provided on a magnet member, and appropriately supply a new developer to the developer carrier.

A development device 20 makes an agitation conveyance member 24 agitate a developer and convey it, has a magnet member 21a fixed including a plurality of magnetic poles, on an inner peripheral side of a sleeve 21j, supplies a developer D to a developer carrier 21 comprising an endless belt 21b provided on a circumference of the sleeve, returns a developer after development into a device body 20a, and separates the returned developer after development from a surface of the endless belt between magnetic poles of the same polarity next to each other. The endless belt is provided with a protrusion part 21e protruding toward an agitation conveyance member side between magnetic poles S and S of the same polarity. A separation surface area 21f for separating the developer on the endless belt is positioned upstream the center of the rotation shaft 24s of the agitation conveyance member in the rotation direction of the endless belt.