Provided is a portable electronic device having a removable hard disk drive in which the hard disk drive is adapted to have a slot-type removable shape, thereby allowing the hard disk drive to be conveniently mounted and used, and when the hard disk drive is detached, power is cut off before detaching the hard disk drive, and when the hard disk drive is mounted, power is automatically supplied after the hard disk drive is completely mounted, thereby preventing damage by a voltage shock. The device includes: a case having a mounting opening on one side thereof, the mounting opening connected to a mounting space inside the case, thereby providing a passage to the mounting space, and the mounting space having a connector disposed on the bottom of the inside of the mounting space; a hard disk drive slidingly inserted into the mounting space through the mounting opening of the case, and having terminals which become in contact with the connector when the hard disk drive is completely mounted; and a power switching unit sensing an operation for attaching or detaching the hard disk drive, thereby cutting off power before detaching the hard disk drive and providing power after mounting the hard disk drive.