Suzaku launched in July 2005 is equipped with the wideband instruments covering 0.3-700 keV. In addition to these main instruments, active shield counters of the hard X-ray detector are designed to be a wideband all-sky monitor (WAM). The WAM is a powerful gamma-ray burst monitor with a wide energy range of 50-5000 keV and with a large effective area of 400 cm2 even around 1 MeV. The paper describes the strategy for the prompt GRB observation with the WAM, and the follow-up observation of X-ray afterglows with the narrow field instruments. So far, the WAM has detected 53 GRBs and half of them were detected simultaneously with other satellites. In addition to that, from at least 8 GRBs, including a bright and hard GRB 051008, it is succeeded to observe significant gamma-ray emission up to 1 MeV. The X-ray afterglow observations were carried out on January 5 and on September 4, 2006. Their results are reported in separate paper.
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