A memory stick includes a casing having a connection member at a top end thereof for connection to a personal item and an opening at a bottom end thereof, a positioning tray insertable through the opening of the casing for positioning in the casing and having an angled upper bending plate extended from a top end thereof and defining with a bottom wall thereof a clamping space and an elastically deformable recessed portion defined in the angled upper bending plate, and a flash memory detachably inserted into the clamping space of the positioning tray and held down in place by the recessed portion.