In this IEC (Interactive Evolutionary Computation) model, designer's implicit preference in making window pattern was acquired as explicit rules of figure pattern, and the possibility of emergent 2-D figure design was shown. In the model, "design world" was made of "primitive" and "design operator", and this "design world" is translated to "critical language" made of first-order logic by using tree structure. The rules of rhythm, proportion and symmetry were composed as dominant pattern in the tree structure, and under this pattern, diverse individuals were acquired.