To dispose a system storing body with excellent arrangement in a space with a projected part in a dwelling by easily adjusting its dimension.

Side plates 11 are cut in accordance with the vertical and horizontal dimensions of the projected part 3 and a back plate 12 is cut in accordance with the vertical dimension of the part 3. A top plate 13 is cut in accordance with the projecting dimension of the projected part 3 so as to leave a back plate fixing groove 131 which is previously arranged in its lower surface part. A shelf plate 15 is fitted to a height position corresponding to the lower surface part of the projected part 3. A cut back plate 121 is fitted between the top plate 13 and the shelf plate 15 by fitting its upper end part to the back plate fixing groove 131 of the top plate 13 and also fixing its lower end part onto the upper surface of the shelf plate 15.