Honeycomb patterned polystyrene film was prepared from a polystyrene chloroform solution including polyion complexes by solvent evaporation under high atmospheric humidity. Formation of the honeycomb pattern was owing to the hexagonally packed water droplets which condensed onto the polymer solution. The pore diameter and the pore depth of the honeycomb pattern were remarkably influenced by the polystyrene molecular weight. A light scattering experiment was conducted to follow the structure formation process. The change of the lattice constant was explained by the behavior of water droplets.