A developing device and an image forming apparatus including the same includes an agitating and conveying unit that receives a developer, and at least one agitating and conveying member to mix and agitate the developer and convey the developer in a developer conveying direction. A developing roller faces a photosensitive drum on which an electrostatic latent image is formed, and attaches the developer to an outer surface of the developing roller. The agitating and conveying member includes a support shaft extending in the developer conveying direction. A plurality of agitation wings disposed on an outer surface of the support shaft to mix and agitate the developer. At least one paddle protrudes from the support shaft in a radial direction and extends along the shaft between adjacent agitation wings. The at least one paddle has a height increasing from an upstream side to a downstream side of the developer conveying direction.