Disclosed are a battery box, a battery cell, a battery, and a method and apparatus for preparing the battery box. The battery box includes a pressure relief region including a first recess arranged at an inner surface of the battery box and a second recess arranged at an outer surface of the battery box, the first recess being arranged opposite to the second recess, wherein a third recess is provided at a bottom wall of the first recess and/or a bottom wall of the second recess, and the pressure relief region is configured to fracture at the third recess, when an internal pressure of the battery box reaches a threshold, to relieve the internal pressure. According to the battery box, the battery cell, the battery, and the method and apparatus for preparing the battery box disclosed in the present application, the pressure relief region is easy to machine.