Provided is a developing device including a developer carrier that holds developer, a supply member that supplies the developer to the developer carrier while agitating the developer, a transport member that is disposed obliquely upward in a vertical direction of the supply member, delivers and transports the developer with agitating the developer through a passageway portion provided at each end portion in an axial direction of the supply member, and a regulating member that is provided at a position corresponding to the passageway portion that delivers the developer from the supply member to the transport member, to regulate movement of the developer from the supply member to the developer carrier.