[en] Effect of the interaction between nuclear magnetic moment and that of electron on the internal conversion coefficient (ICC) is discussed. Nucleus and electron are assumed to form a single quantum-mechanical nucleus-electron system. The equation Hsub(psi)=epsilonsub(psi) is solved by the method of perturbation of stationary states. Analytical expressions for ICC of magnetic and electrical transition are obtained. Numerical calculations have been run on a computer in the case of point nucleus without account for screening. Results point out that taking into account the nucleus magnetic moment leads to better agreement between theoretical and experimental values of ICC