An image forming apparatus includes a revolver type developer, and prevents toner stored within the revolver type developer from being adversely influenced by heat from a fixing unit. As one feature, the revolver developing unit is intermittently rotated when the image forming apparatus is in a stand-by state. As a further feature, the revolver developing unit is rotated at a very slow continuous speed when the image forming apparatus is in a stand-by state. As a further feature, the intermittent rotation and the slow continuous rotation of the revolver developing unit can be stopped if the temperature of the fixing unit falls below a predetermined value.