To provide a developing device, which includes: a first conveying passage through which a developer including a toner and a magnetic carrier is conveyed; a first conveying member disposed in the first conveying passage for conveying the developer in a predetermined whilst agitating; a toner supply port for supplying toner into the first conveying passage; and a multiple number of electromagnets arranged in the upper part of the first conveying passage and on the downstream side of the toner supply port with respect to the developer's direction of conveyance for creating magnetic fields inside the first conveying passage along the developer's direction of conveyance, and which can improve agitation performance and conveying performance of the developer without extremely increasing stress acting on the developer, as well as providing an image forming apparatus and developer conveying method using the device.