A folding assembly box comprising: vertical corner hinge frames disposed in corners of the box, wherein the vertical corner hinge frames are unfolded at an angle to form the respective corners of the box, and are hinged in the opposite direction to the direction where the vertical corner hinge frames are unfolded; first top and bottom horizontal frames disposed to connect upper and lower ends of the vertical corner hinge frames facing each other; vertical middle hinge frames disposed between the vertical corner hinge frames facing each other at both sides thereof in parallel to the vertical corner hinge frames, wherein the vertical middle hinge frames are unfolded together with the vertical corner hinge frames at both sides thereof, and hinged in the opposite direction to the opposite direction where the vertical corner hinge frames are unfolded; second top and bottom horizontal frames disposed to connect upper and lower ends of the vertical corner hinge frames facing each other with the vertical middle hinge frame interposed therebetween; first panels, each having side edges inserted between the vertical corner hinge frames facing each other and upper and lower edges inserted between the first top and bottom horizontal frames facing each other; second panels, each having side edges inserted between the vertical corner hinge frame and the vertical middle hinge frame facing each other and upper and lower edges inserted between the second top and bottom horizontal frames facing each other; a corner clamp for fixing the vertical corner hinge frame and the first top and bottom horizontal frames and a corner clamp for fixing the vertical middle hinge frame and the second top and bottom horizontal frames; characterised in that the vertical corner and middle hinge frames (50, 60) and the first and second top and bottom horizontal frames (80, 81) have inclined cut ends at both sides thereof; and the cut ends of the vertical corner and middle hinge frames (50, 60) are engaged and coupled to the cut ends of the first and second top and bottom horizontal frames (80, 81) so as to correspond to each other. vertical corner hinge frames disposed in corners of the box, wherein the vertical corner hinge frames are unfolded at an angle to form the respective corners of the box, and are hinged in the opposite direction to the direction where the vertical corner hinge frames are unfolded; first top and bottom horizontal frames disposed to connect upper and lower ends of the vertical corner hinge frames facing each other; vertical middle hinge frames disposed between the vertical corner hinge frames facing each other at both sides thereof in parallel to the vertical corner hinge frames, wherein the vertical middle hinge frames are unfolded together with the vertical corner hinge frames at both sides thereof, and hinged in the opposite direction to the opposite direction where the vertical corner hinge frames are unfolded; second top and bottom horizontal frames disposed to connect upper and lower ends of the vertical corner hinge frames facing each other with the vertical middle hinge frame interposed therebetween; first panels, each having side edges inserted between the vertical corner hinge frames facing each other and upper and lower edges inserted between the first top and bottom horizontal frames facing each other; second panels, each having side edges inserted between the vertical corner hinge frame and the vertical middle hinge frame facing each other and upper and lower edges inserted between the second top and bottom horizontal frames facing each other; a corner clamp for fixing the vertical corner hinge frame and the first top and bottom horizontal frames and a corner clamp for fixing the vertical middle hinge frame and the second top and bottom horizontal frames; characterised in that the vertical corner and middle hinge frames (50, 60) and the first and second top and bottom horizontal frames (80, 81) have inclined cut ends at both sides thereof; and the cut ends of the vertical corner and middle hinge frames (50, 60) are engaged and coupled to the cut ends of the first and second top and bottom horizontal frames (80, 81) so as to correspond to each other.