A developing device includes a developing container, a first agitating/conveying member, a second agitating/conveying member, a developer supply member, a supply port, and a supply section. The developing container is separated into a developer supply passage, a first conveying chamber, and a second conveying chamber, which are arranged substantially parallel to one another. The supply section is disposed between the developer supply passage and the first conveying chamber, and through the supply section, the developer is supplied from the developer supply passage into the first conveying chamber. The supply section is disposed upstream from a downstream-side end portion of the developer supply passage but downstream from the supply port with respect to a developer-conveying direction of the developer supply passage, and via the supply section, the developer supply member supplies the developer into the first conveying chamber in a direction opposite to a developer-conveying direction of the first conveying chamber.