An image forming apparatus includes: a main casing; a photosensitive drum rotatable about an axis extending in a first direction; a developing cartridge; a transfer unit; a solvent cartridge accommodating solvent for dissolving toner; an applicator applying the solvent to the toner on a sheet; and a cover movable between an open position and a closed position. The developing cartridge and the solvent cartridge are detachably attachable to the main casing independently of each other. The developing cartridge and the solvent cartridge are positioned between the applicator and the cover in a second direction crossing the first direction, and the solvent cartridge is positioned closer to the applicator than the developing cartridge is to the applicator in a state where the developing cartridge and the solvent cartridge are attached to the main casing and the cover is at the closed position.