The invention provides a volume-adjustable file box mainly used for archives of such enterprises and public institutions as government offices. The volume-adjustable file box is provided with a chute in a box body; an up-down adjusting device can move up and down in the chute; and a screw of the up-down adjusting device can be fastened with and separated from the chute to realize the volume adjustment of the file box. The left edge, the front edge, the right edge and the back edge are respectively bonded with magnets on the box body through magnets to realize total closing of the box body. Files in the file box can be tightly pressed by a hoop piece on the up-down adjusting device. The volume-adjustable file box is simple in structure and convenient for use, can adjust the volume of the file box, can effectively prevent the disordered problem of files in the file box, and effectively reduces the labor intensity of file management staff.