Abstract: A foldable storage device contains a body ultrasonic seamless connected and including a bottom end and side walls, among the bottom end and the plural side being defined an accommodating space. A peripheral side of an upper end of the body connects with a frame, the body has a rigid plate with a flange. Two support racks are mounted on two opposite walls of the accommodating space and coupling with at least one connecting sleeve and the frame. Each connecting sleeve has an upper tube with a cutout for inserting the frame and a lower tube. Two ends of each support rack are inserted into two lower tubes, a length of each support rack is greater than or equal to a depth of the accommodating space, each support rack is rotated inwardly to face to one side wall of the body or is rotated outwardly to engage with the flange.