The potential-energy surfaces of the total, pi, and sigma electrons are obtained concerning deformation of benzene : it is shown that there are countless numbers of reaction coordinates for distortion that either lower or increase the pi energy. The minimum-energy path (MEP) was found for the distortion from D-6h to D-3h and was not one previously investigated. Along such an MEP, the role of the pi electrons seems to be reversed; i.e., the pi electrons are most stable at the D-6h symmetry. The reason for the low frequency of the B-2u vibrational modes is given. The molecular geometry has been distorted to perturb the pi-electronic structure in the study of the relationship between the pi-electronic structure and the pi energy, a component of the total energy. However, this method was shown to be inappropriate, since even if the changes of the geometry and total energy are small, those of partitioned energies can enormously fluctuate due to the energy-relationship given by the molecular virial theorem.