An image forming device includes: a main casing; a plurality of photosensitive bodies; a first roller; a second roller; an endless belt; a plurality of primary transfer members; a cleaning unit; and a secondary transfer member. The cleaning unit is configured to collect residual toner remaining on the endless belt, and detachable from and attachable to the main casing. The secondary transfer member is provided at the cleaning unit such that the secondary transfer member is detachable from the main casing upon detachment of the cleaning unit from the main casing and attachable to the main casing upon attachment of the cleaning unit to the main casing.