The behavior of the state of liquid water is studied by means of changes of refractive indices of the visible light region based on the data of Tilton. A fairly simple model is assumed for the structure of liquid water. Lorentz-Lorenz's formula is employed for the molecular structure of liquid water. The visible light region is taken between the ultra-violet and the infra-red regions, and it is apart from the fundamental absorption bands or lines in both regions. Therefore, even though the contributions from the both regions to the behaviors of the refractive index may play a dominant role, but they can be treated in the simple form of Lorentz-Lorenz's formula. It is found that the behaviors of induced dipoles of liquid water are closely related with molecules and electron clouds. It is also found that when our improved theory is applied, many models of liquid water which have been proposed by many investigators can be understood consistently without any contradiction. It is shown that when ice transforms to liquid water the deformation of electron clouds occurs; the long-range force of water molecules corresponding to melting is changed.