In a developing device including a developer tank and a developing roller, an internal space of the developer tank is divided into a first conveying path, a second conveying path, a first communication path and a second communication path, by a partition wall. A first developer conveying section which conveys a developer in the developer tank in a conveying direction X is disposed in the first conveying path. A second developer conveying section which conveys the developer in the developer tank in a conveying direction Y is disposed in the second conveying path. The first developer conveying section includes a plurality of inner spiral blade pieces, a rotation tube, an upstream spiral blade, a downstream spiral blade, support members, and a first gear.