Photoisomerization of the rhodopsin chromophore is one of the typical nonadiabatic transitions. We have proposed a new dynamical theory of photoisomerization of the chromophore based on quantum mechanics. We have considered the transient excited state DES (deformed excited state : Psi(D)) of electrons, which has different lengths for stabilization from those in the excited state immediately after the absorption of light, together with the lowest electronic state VGS (virtual ground state : Psi(V)), which has the same bond lengths as Psi(D). We have also considered the normal vibrational states {U-rj(Theta)} associated with these transient electronic states {Psi(r)(Theta)} (Theta represents the angle of cis-trans isomerization). With these preliminary assumptions, the nonstationary state Phi(t) of the chromophore has been expressed as an expansion in {Psi(r)(Theta)U-rj(Theta)}, and the time-dependent equation for its coefficients {b(rj)(t)} has been derived rigorously by explicitly taking into account the kinetic energy of atomic cores. On these bases, in the present study we calculate a transient electric field caused by the change of the net charges in the chromophore during photoisomerization. To examine the effect of this field on the protein moiety around the chromophore, we calculate by way of example the interaction between formamide and a constant electric field. The results demonstrate that the net charges in formamide are considerably affected by the constant electric field. We then apply this calculation to a bacteriorhodopsin model and also demonstrate the change of the net charges in the amino acids near the chromophore. Finally, we point out that the change of the net charges in the amino acids and the vibrational-vibrational interaction between the chromophore and its surrounding opsin are crucial.