A memory card locking device is provided. The memory card locking device includes an external card reader having a card slot in which a memory card is allowed to be inserted. The external card reader includes a main controller. The main controller is configured to receive a locking instruction from an application, and execute a locking program on the memory card to lock the memory card according to the locking instruction. When the memory card is locked, any device other than the external card reader cannot read and identify the memory card, and thus cannot look up and access data stored in the memory card.