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There is an increasing demand of high-value-added workpieces that generally have three dimensional and complex shapes such as aircraft parts. In complex parts machining, workpiece shape and stiffness change greatly during a rough machining operation and induce workpiece displacement and vibration that strongly affect machining accuracy and tool life. However, it is difficult to automatically determine machining process parameters such as cutting sequence, tool paths and cutting conditions by using a commercial CAM system because there is a large number of combinations. Therefore, in order to improve the efficiency of complex parts machining, it is necessary to clarify these tacit knowledges and to formulate the implicit machining know-how owned by skillful experts. The authors have been proposed a determination method of complex workpiece shapes during a rough machining operation based on topology optimization. In the method, topology optimization is used to calculate workpiece shapes to ensure the stiffness by dividing a rough machining operation into several steps. However, the operation planning has not been adequately considered to determine machining process parameters. Moreover, it is necessary to repeat the calculation of topology optimization because a rough machining operation is divided into many machining steps. Thus, in this study, a determination method of cutting sequence is proposed by using the design variables obtained in the calculation process of topology optimization of workpiece. In order to estimate the machined shape based on the proposed cutting sequence, cutting experiments are conducted. The results show the effectiveness of the proposed cutting sequence to reduce the deformation of workpiece during a rough machining operation of complex parts machining.