The disclosure relates to a support structure of a wind turbine, in particular a main frame. An object is to develop an ideal load distribution and stiffness distribution of the main frame with a least possible use of material. The main frame is intended optimally to fulfill the requirements with respect to the operating and extreme loads and the stiffness for the given space conditions inside the nacelle. The main frame has a top, bottom, front and rear side, and includes a circumferential annular wall between the bottom and the top side. The main frame includes two lateral portions of the wall that extend between the front side and the rear side of the main frame. Additionally included are two lateral flanges on the top side of the main frame, a plurality of arms being arranged inside the wall. The arms are connected to the wall via a box profile.