Porous structures are interesting structures that can express various functions depending on their morphology. In recent years, there has been a great deal of interest in a design and fabrication process in which the optimal shape of a porous structure suitable for a particular purpose is found beforehand, and then it is directly fabricated by additive manufacturing. However, when using the conventional topology optimization method, theoretically thicker members tend to appear (Fig. a), and special forms in which the porous structure is distributed throughout the entire structure cannot be obtained. For this reason, a new method has been proposed that imposes a local volume constraint in addition to the overall material volume constraint to make it easier to obtain a porous structure (Fig. b). However, the resulting porous structure is prone to stress concentration and buckling of the member. In this study, we are developing a stress constraint method using p-norm and a design method for porous structures that can improve buckling load in a simple way to reduce this problem.