Abstract Time-resolved fluorescence spectra of 4′-N,N-diethylamino-3-methoxyflavon in ionic liquids have been measured by using a Kerr gate method and a streak camera at different excitation wavelengths, 370, 400, and 425 nm. Fluorescence spectra showed a shift to longer wavelength with longer delay time after photoexcitation. The peak position of the fluorescence spectrum at each delay time was evaluated by simulating the spectrum by a log-normal function. It was found that the peak shift of the fluorescence at the early delay time was larger for the shorter excitation wavelength (blue side of the absorption), and in the longer delay time they coincide to the same value. The time profile of the peak position was well simulated by the sum of an exponential function and a stretched-exponential function. The average relaxation times evaluated by the integration of the longer relaxation function were weakly dependent on the excitation wavelength, and they were correlated with the viscosity of the solvent. The relation with the excitation wavelength dependence of the excited state intramolecular proton transfer reaction of 4′-N,N-diethylamino-3-hydroxyflavon is discussed.