An electrical adapter assembly for connecting a first hard disk drive and a second hard disk drive is provided. The electrical adapter assembly includes a connector capable of electrically inserting into the first hard disk drive, a printed circuit board (PCB) module electrically connecting the connector, and a loading member for loading the first hard disk drive. The PCB module includes a chip for controlling data transfer between the first hard disk drive and the second hard disk drive. The loading member includes a base and at least two guiding portions pivotally attached on the base to allow the first hard disk drive to be able to slide between the at least two guiding portions.