There is provided a drug refilling apparatus. The apparatus includes a main body on which a drug cartridge is mounted, a cartridge mounting unit installed on a top surface of the main body to allow the drug cartridge mounted thereon, an unfastening unit unfastening a fastened state of a cover included in the drug cartridge, and a cartridge locking unit locking or unlocking the drug cartridge while the drug cartridge is being mounted on the cartridge mounting unit.