A developing device includes a non-magnetic rotatable sleeve of a developer bearer to bear developer and a development electric field generator to generate a development electric field between the image bearer and the developer bearer by applying a development bias to the developer bearer. The developing bias is an AC bias generating an AC electric field therebetween. The magnetic carrier includes a plurality of fine particles each covered by a covering layer made of prescribed material having a volume resistivity equal to or more than 1012 [Ω·cm] having a prescribed particle diameter equal to or less than 100 [nm]. Each of the a plurality of fine particles has a total volume resistivity equal to or less than 105 [Ω·cm]. The magnetic carrier has a total volume resistivity equal to or more than 1012 [Ω·cm].