This study demonstrates the analysis and optimization of a gantry-type 5-axis CNC machine tool. Critical points in designing and optimizing a large-scale gantry are discussed. Moreover, the FE analysis results of the initial gantry design are shared with detailed discussion, and the measurement results on structural dynamics are shown together with the FE results. In addition, topology optimization is applied to the gantry component of the machine tool and the optimized gantry structure is presented. It is shown that the dynamic modes of the gantry structure can be improved by topology optimization.