This paper shows that the WKB quantization rule is suitable for Andreev bound states in nonuniform superconductors. We consider nonhomogeneous superconductivity gap functions $\mathrm{\ensuremath{\Delta}}(x)$ superconductors with Bogoliubov quasiparticle energy $E$, Fermi level ${E}_{F}$, and total momentum $\mathbf{p}$ at ${E}_{F}+E$. The well of slowly varying $|\mathrm{\ensuremath{\Delta}}(x...