A toner supply device for supplying toner to a developing unit, includes: a toner cartridge for storing toner; and a toner feed device disposed adjacent to the toner cartridge and composed of a casing for reserving the toner supplied from the toner cartridge and first and second toner agitator shafts for agitating and conveying the toner inside the casing, and is constructed such that the toner feed device agitates the toner supplied from the toner cartridge first, then feeds the agitated toner to the developing unit.