A document organizer includes a base frame, a rear frame, a front frame, and a plurality of dividers. The base frame includes a plurality of base boards and base connecting boards. Each base board has a first folding line. The rear frame includes a plurality of rear boards and rear connecting boards. Each rear board has a third folding line. The front frame includes a plurality of front boards and front connecting boards. Each front board has a fifth folding line. Each divider has a fourth coupling portion, a fifth coupling portion, and a sixth coupling portion correspondingly couple to a first coupling portion, a second coupling portion, and a third coupling portion. The base frame, read frame, front frame, and the dividers cooperatively define a plurality of storage space therebetween. As a result, the document organizer is collapsible to save space and materials.