A complementary division condition determining method and program and a complementary division method able to propose the optimum complementary division conditions for suppressing pattern displacement and mask destruction, wherein an internal stress of a mask is determined based on a displacement of a peripheral mark in a case when forming an opening in the mask and this value is used for first analysis (step ST12), pattern displacement and stress concentration occurring due to openings of split patterns are analyzed based on a first analysis model in a first analysis (step ST13), and a displacement due to external force of the membrane between the split patterns is analyzed in a second analysis (step ST14).