Method for Manufacturing Case of Battery Module and Case of Battery Module

A method for manufacturing a lower case of a battery module includes an extrusion molding operation in which a metal material is extruded to mold a cooling plate member and a sidewall member of a battery module; a forging operation in which an internal surface of the cooling plate member is pressed with a punch, having an edge of a lower end provided vertically to form an accommodation groove; and a forming operation in which an embossed piece, protruding to an external surface of the cooling plate member by forming the accommodation groove, is removed.