To understand the mechanism of isotope effect in the nitrogen vibrational levels in the nitrogen discharge plasmas from the viewpoint of atomic and molecular processes in plasmas, vibrational populations of N2 vibrational levels is numerically modeled and calculated. What should be noted is that the isotopic effect is considered in the simulation to find the isotopic effect of vibrational excitation kinetics between 14N2 and 14N15N. Remarkable isotope effect was found between them, and the potential of its practical application to industrial 15N enrichment is discussed numerically.