Two-color multiphoton ionization spectra of gaseous nitric oxide via a single Zeeman sublevel in the A (2)Sigma(+) (v=1) state were measured in magnetic fields up to 10 T. The Zeeman effect on high-lying Rydberg states (n greater than or equal to 28) and Landau levels above an ionization potential corresponding to the v=1 vibrational level of cation were observed. Landau level spacing gradually decreased with increasing energy, reflecting the transition from the quasi-Landau level to the Landau level. The broadness of the band due to the transition to the Landau level is discussed based on ionization mechanism.