Provided are a lower case body, a case having the same, a battery pack, and an electric device. The lower case body is used for the battery pack, and the lower case body includes: a bottom plate, the bottom plate extending in a first direction in a horizontal plane, two side edges of the bottom plate in a second direction in the horizontal plane being provided with first connecting parts, the first connecting parts being configured to be connected to an upper case body of the battery pack, and the first direction intersecting the second direction; and first side plates, two first side plates being provided and arranged at two ends of the bottom plate in the first direction, respectively, the first side plates being vertically disposed, and a lower end of the first side plate being connected to the bottom plate by full welding.