Synchrotron radiation Sm-149 Mossbauer spectroscopy in the energy domain has successfully been carried out on Sm2O3, SmBe13, and SmB6. The isomer shift values were determined in these compounds to discuss their Sm valence state. We also investigated the time window effect on spectra, which is useful for measuring spectra with "high-energy-resolution". This effect makes it possible to discuss the frequency of valence fluctuation in Sm compounds as well as determine Sm valence state precisely using the Sm-149 Mossbauer effect. We discussed the fluctuation of the Sm valence in SmB6.