A frame structure and a method of manufacturing a body frame that is divided into small assemblies to facilitate the carriage and storage of articles and individuals and the manufacturing efficiency. A body frame is divided into three, namely, a front assembly having a closed loop structure, an engine support system assembly having a closed loop structure and a rear suspension support system assembly having a closed loop structure. The front assembly and the rear suspension support system assembly are connected to the engine support system assembly to form the body frame. The small assemblies have a closed loop structure whereby the rigidity is enhanced, and the shape is also stabilized. Therefore, the accuracy management can be performed.