The invention relates to a rectangular paper box. A making method for the paper box comprises that: a piece of rectangular paper is divided into five parts by four longitudinal lines, wherein three parts have equal length, namely the length of a box body, and two parts have equal length, namely the width of the box body; the paper is divided into three parts by two transverse lines, wherein an upper fold line is a reverse fold line, the lower fold line is a positive fold line, the upside of the reverse fold line is provided with three rectangles and two squares, the height between the two fold lines is the height of the box, and the lower height is slightly shorter than the middle height; the lower part of figure 1 is positively folded; figure 2 is reversely folded for an angle of 90 degrees along the four longitudinal lines respectively, and two ends are interpenetrated and overlapped; 31 is inwards folded for 90 degrees, and halves of adjacent 32 and 33 are inwards folded for 180 degrees along a folding mark; 41 is inwards folded for 90 degrees, and halves of adjacent 42 and 43 are inwards folded for 180 degrees along a folding mark; 51 and 52 are reversely folded for 90 degrees and inserted into a lower interlayer; and figure 6 is overturned up and down, and a box opening faces upward. The whole piece of paper is folded into the rectangular paper box; the length, width and height can be designed freely; four walls of the paper box can be arranged into double layers or multiple layers; and the paper box is thick and firm, simple to manufacture, and easy to learn and manufacture.