Preventing an electric connecting box having an upper cover and a lower cover, which can prevent the upper cover from approaching the lower cover over a limit when an electric component is mounted on the upper cover, the electric connecting box 1 is provided with an upper cover 2, a lower cover 3, a middle cover 4, a printed wire board 5, a wiring board 6 and a shield plat 7. The upper cover 2 is mounted on the lower cover 3. The lower cover 3 has a first strut 20 abutting on the shield plate 7. The first strut 20 supports the upper cover 2 through the shield plate 7 and the wiring board 6.