A folding box includes a rectangular base, two side boards, two end boards, and two mounting apparatuses mounted to each side board. The base includes a bottom plate, two side plates protruding up from two opposite sides of the bottom plate, and two end plates protruding up from two opposite ends of the bottom plate. The side boards are rotatably connected to the two side plates. The end boards are rotatably connected to the two end plates. Each mounting apparatus includes a first inserting member slidably installable on the corresponding side board. A flange protrudes inward from each end of each end board. A protrusion protrudes inward from each flange. Each protrusion defines a latching hole aligning with the corresponding first inserting member. Each first inserting member is inserted into the corresponding latching hole, to connect the side boards to the end boards.