In order to automate and reduce the number of setups, a rotary table is added on a 3-axis machining center to increase the number of multi-axis machine tools. While the accuracy of the rotary table has been improved, the influence of the structure errors on the machining accuracy is too huge. The degree of parallelism and coaxiality between the three translational axes and the rotation axis of the rotary table affect to a serious problem of machining accuracy. In this research, the effect of structure errors of the rotary table on the machining accuracy is mathematically analyzed by FormShape-Function theory. Machining errors of cylindrical processing are expressed with structure errors in these series of simulations.