A plurality of developing units is disposed beneath photosensitive drums for supplying toner to the photosensitive drums. A mounting member detachably mounts the developing units and is configured to be pulled out from the main casing. A supporting member has an upstream end portion in a pulling direction that the mounting member is pulled outward from the main casing and is pivotably supported on the main casing about the upstream end portion. The mounting member is slidably supported on the supporting member in the pulling direction. The supporting member is configured to pivot with the mounting member between a first position where the developing units are capable of supplying toner to the photosensitive drums and a second position where the developing units separate from the photosensitive drums. The mounting member is configured to be pulled out from the main casing if the support member is in the second position.