The present invention is to provide an electric connection box for preventing movement of a large size relay and improving reliability of electric connection. The electric connection box includes a main body, a guide wall disposed on the main body for retaining an electric component, a protrusion disposed on an inner face of the guide wall for preventing movement of the electric component. The guide wall has an upper protrusion at an upper end portion thereof and a lower protrusion at a lower end portion thereof, and the upper protrusion extends toward the electric component more than the lower protrusion and at least contacts with or approaches to the electric component. The guide wall is higher than the center of gravity of the electric component and the protrusion is positioned above the center of gravity of the electric component. An electric connection box includes a first cover for retaining an electric component and a second cover having a locking member, wherein the locking member extends vertically and passes through the first cover for locking the electric component. The second cover has a middle plate for arrangement of a busbar and the locking member extends vertically through the middle plate.