The present invention is directed to a folder type file tray assembled from a single paperboard blank. The file tray can be flattened to a reduced size during storage or transportation. It can also be assembled into different forms for different usage. The first form of file tray is an open-top box with a front opening for usage as a conventional file tray. The second form of file tray is an open-top box without a front opening, i.e., surrounded by four side walls for usage as a desk-top tool box. The third form of file tray is an open-top box with a foldable closing lid for usage such as a storage box. Additionally, the file tray of present invention can be stacked up directly to each other in multiple numbers without additional means of support. The file tray of present invention has low material and manufacturing costs. If needed, one side of paper blank can be laminated with higher quality paper or decorative material to enhance the appearance of file tray of present invention.