In order to attain dynamically optimum design of machine tools which would have minimum chance of machining chatter, an approach based on energy balances of a mathematical system at the resonance is developed and analysed theoretically. This method aims that the maximum compliance of the tool-work relative displacement in the direction normal to cut surface caused by the cutting force at the cutting point must be minimum across all frequency ranges. Using the computer simulations of machine tool structures, modal flexibilities are computed, by the magnitude of which the chance of regenerative chatter is judged. Focusing on the particular mode where the modal flexibility is predominantly high, and by consulting with the energy distribution through the complete structure at the mode, a design change is proposed such that the static flexibility is small and evenly shared by modal flexibilities in many modes. The outline of a computer program is described and demonstrated by computed and experimental results on a practical machine structure.