This application relates to the field of battery technologies, and provides a battery module and a manufacturing method thereof. The battery module includes: two or more battery groups, each battery group including two or more battery cells; a module frame, including end plates and side plates, wherein the end plates and the side plates form an accommodating cavity for fixing the battery groups; a middle plate, wherein the middle plate is disposed between two of the battery groups, and is provided with an accommodating groove inside; and a cell management unit, disposed in the accommodating groove of the middle plate and connected to a sampling line of the battery cells. A cell management unit in the accommodating groove inside the middle plate can reduce the chance from failing under swelling pressure of the battery cells.