In order to elucidate photofading mechanism of aerated alcoholic solution of model magenta dye with carbonyl compound (CCPD), 1) effect of acid on photofading of alcoholic solution of model magenta dye with CCPD, 2) effect of NaOH, 3) effect of oxygen concentration, 4) absorption change of the photolytically faded solution by keeping in dark, addition of NaOH-EtOH solution and light irradiation after unsealing, are examined at various conditions. Also photofadingproduct in aerated alcoholic solution of model magenta dye with CCPD is examined by mass spectroscopy. It is confirmed that photofading of the solution is initiated by ketyl radical of CCPD and following reactions resulted in formation of oxygenated compound and degradation of the dye are started probably from mono-hydrogenated dye radical in the same way as aerated solution of model cyan dye. Moreover it is estimated that the most part of the difference in details between fading reactions of model magenta and cyan dyes is caused by higher reactivity of mono-hydrogenated radical and leuco-form of magenta dye with oxygen in comparison with cyan dye.