A medium storage box according to an embodiment includes: a cassette body having a storage space in which a medium is stored; a cassette door coupled to the cassette body to open or close the storage space; a door opening detection unit for generating an open detection signal when the cassette door is opened; a microcomputer for determining that the cassette door is opened when receiving the open detection signal, and for storing the determined opening information of the cassette door in a cassette memory; and a battery for supplying power to the door detection unit and the microcomputer, wherein when the open detection signal is generated in the door opening detection unit, the battery supplies power to the microcomputer.