A developing unit for transferring toner onto a latent image on an image
carrier so as to develop the latent image includes a toner carrier, an
electric field generator and a separating force applicator. The toner
carrier including a plurality of electrodes disposed along the surface
thereof and insulated from each other transports the toner to a
developing area facing the image carrier. The electric field generator
applies a periodic voltage to the plurality of electrodes of the toner
carrier so that an electric field is generated on the toner carrier
surface to cause the toner charged to a given polarity and borne on the
surface of the toner carrier to hop. The separating force applicator
applies a separating force to separate the toner on the toner carrier
from the surface thereof outside the developing area. The separating
force applicator is disposed separately from the electric field
generator.