AbstractThe locality of conformational state with relation to the asymmetry in potential is proved. The adequacy of harmonic approximation of conformation wave function is discussed. Then, on the grounds of the rigorous definition of the conformation‐vibrational state, the role of vibration in the information transmission and cooperativity is discussed by the calculation of statistical mechanics. In the rest of this article, the conformational change as a quantum transition is investigated in detail. The viewpoint of conformational transition with respect to electronic motion is stressed. On the basis of proposed selection rules, the approach to the conformational change that consists if multiple steps is clarified.