Through the analytic solutions of the Bogoliubov de Gennes (BdG) equations the effect of a static and homogeneous magnetic field applied parallel to the interface of an NIS (N: Normal metal, S: superconductor and I: Insulator) junction on the differential conductance is calculated. For a d xy - symmetry we obtain zero bias conductance peak that can be split by a magnetic field. The shift of the zero bias conductance peak depends on the spread (beta) of the tunneling electrons in k space, on the magnitude of the applied field H and on the ratio between the Fermi energy of the superconductor and the normal region, E FS/E FN. Finally we estimate the minimum value of the magnetic field, Hmin, that splits the zero bias conductance peak. In general Hmin depends on beta, E FS/E FN, the strength of the insulating barrier Z and on the temperature T.