Functionally graded material (FGM) has continuous and functional flexibility of volume fraction distribution of constituent particles which leads to superior thermomechanical performance to classical laminated composite materials.[1] Since the thermomechanical characteristic of the FGM depends on the volume fraction distribution, it is important to select appropriate volume fraction distribution satisfying the desired performance and boundary conditions.To find the proper volume fraction in FGM meeting the required performance, many researches on design optimization of FGM have been carried out.[2-5].