Thanks to the development of additive manufacturing technology, it is becoming possible to produce materials with desired mechanical properties defined by their periodic microstructures. To design optimal microstructures, multi-scale topology optimization has been paid attention to in many engineering fields. For example, Kato et al. [1] proposed a multi-scale topology optimization method based on decoupling micro-macro analysis. This efficient method has reduced computational cost and made multi-scale designing more feasible compared with the previous approaches. However, compute time and memory requirements are still high, and these prevent practical use such as high-resolution 3D analysis for precision modeling and non-linear analysis assuming actual materials. In most approaches, including the above, the finite element method (FEM) is used to analyze periodic microstructures, but this study focused on an alternative approach using the fast Fourier transform (FFT) by Moulinec and Suquet [2]. Its efficient algorithm and point-wise discretization are highly compatible with topology optimization. In this study, as a basic problem, we deal with topology optimization of microstructure for maximizing ductility (energy absorption performance). For simplicity, no specific macrostructure is assumed and a unit cell is subjected to forced strain directly. Through several sample analyses, we demonstrate that the proposed method with FFT can obtain almost the same optimized topology as the conventional method with FEM. We also discuss the filtering approach to avoid the loss of accuracy caused by the Gibbs phenomenon. REFERENCES [1] Kato J., Yachi D., Terada K., Kyoya T. Topology optimization of micro-structure for composites applying a decoupling multi-scale analysis. Struct. Multidisc. Optim., Vol. 49 (4), pp. 595-608, 2014 [2] Moulinec H., Suquet P. A numerical method for computing the overall response of nonlinear composites with complex microstructure Comput. Methods Appl. Mech. Engrg., Vol. 157, pp. 69-94, 1998