The storage box is formed from a sheet provided with a plurality of folding lines defining a parallelepiped provided with six faces, one of said face being a hinged lid (2), and it is characterized in that the opposed face to said hinged lid comprises a first sector (1a) provided with an oblique folding line (7a) that defines a first joining zone (8a); a second sector (1b) also provided with an oblique folding line (7b) that is joined to said first sector (1a) in said first joining zone (8a); a third sector (1c) provided with an oblique folding line (7c) that defines a second joining zone (8c); and a fourth sector (1d) that is joined to said third sector (1c) in said second joining zone (8c).It permits to obtain a box that can be mounted by itself.