An apparatus for measuring the fluorescence excitation spectra of gaseous molecules in very high magnetic fields generated by a water-cooled resistive magnet has been developed. Spectra due to the A(2)Sigma (+) (upsilon' = 0)-(XII)-I-2 (upsilon " = 0) transition of NO were measured in magnetic fields up to 25 T. The spectra show complicated line structures due to large Zeeman splitting in both the A(2)Sigma (+) and (XII)-I-2 states. The transition energies and line intensities were calculated using Hund's case (a) basis set to assign the observed lines.