A hard disk retaining apparatus includes a main body and an indicating module is installed inside the main body, the indicating module includes a display button, a trigger button, and a display unit. When the hard disk drive is installed into the main body, the hard disk drive contacts the trigger button, pressing the display button, the display unit can display if the hard disk drive is installed into the hard disk retaining apparatus. When the hard disk drive is not installed into the main body, the display unit does not work.