A developing unit includes a developer bearing member that rotates and bears a developer including a toner and a carrier. A controller switches between a first mode and a second mode based on information which influences a toner charging amount. In the first mode, the developer bearing member rotates during a predetermined operation period from a command of an image forming operation until start of forming the electrostatic latent image. Meanwhile, in the second mode, a total number of rotations of the developer bearing member during the predetermined operation period is smaller than that in the first mode.