The invention relates to a developing device used for an image forming apparatus adopting a two-component developer containing a carrier and toner, and an image forming apparatus including the same. The developing device of the present disclosure has a developing housing, a developer bearing member, a toner bearing member, a bias applier, a bias controller, and a rotation driver. With respect to a duty ratio of the alternating current bias of a polarity with which the toner is moved from the developer bearing member to the toner bearing member, a second duty ratio that is a duty ratio of the collection bias is set to be smaller than a first duty ratio that is a duty ratio of the development bias. When a transition is made from the development operation to the collection operation, in a state where the developer bearing member and the toner bearing member are being driven to rotate, the bias controller performs control so that the bias applier applies the alternating current bias having a third duty ratio that is smaller than the first duty ratio and larger than the second duty ratio. According to the invention, the developing device which limits dispersion of a toner between a developing roller and a magnetic roller and an image forming apparatus having the developing device are provided.