Bulbul et al. (2014) reported the detection by XMM-Newton instruments of an unidentified X-ray emission line at an energy around 3.5 keV in spectra for the Perseus and other clusters. They argued for a possibility of the decay of sterile neutrino, a dark matter candidate.We examine Suzaku X-ray Imaging Spectrometer (XIS) spectra of the Perseus cluster for evidence in the 3.5keV line and other possible dark matter features in the 2-6 keV energy band. In order to search for and constrain a weak line feature with the XIS, observations of the Crab Nebula are used to evaluate the system's effective area. We found no line feature at the claimed position with a systematic line flux upper limit at a half (1.5 eV in line equivalent width) of the claimed best-fit value by Bulbul et al. We discuss this inconsistency in terms of instrumental calibration errors and modeling of continuum emission. Other dark matter search in X-ray are also introduced. Future prospects for high-energy resolution spectroscopy with ASTRO-H are presented.