Aminoguanidine and alkoxyguanidine compounds are described, including compounds of the Formula VII: . The developing unit includes a first supported portion configured to be swingably supported with respect to the image bearing member unit, a second supported portion provided configured to be swingably and slidably supported with respect to the image bearing member unit, and a regulated portion configured to be capable of contacting a regulating portion provided on the image bearing member unit. By this, the initial value of the target air-fuel ratio can be suitably set at a start time of execution of the air-fuel ratio FB control during the supply of the secondary air.