Box file

A box file, comprising:

• a first box forming component having a pair of side walls and at least one bottom plate and at least one back wall provided between the side walls in an opening state into the air at least at a top portion thereof;
• and a second box forming component having one side wall formed into a shape symmetrical to or a similar figure smaller than the side wall of the first box forming component and in a parallel state with reference to the side wall of said first box forming component and at least one bottom plate and at least one back wall provided between edges of the side walls, so that the bottom plates and back walls of the first and second box forming components are adapted to be coupled together and a first box forming component and a second box forming component are provided such that an intervals between the side walls thereof are reciprocally closed or departed and the respective side walls are adapted not to move in surface directions mutually.