The Bayesian posterior probability density vs. trial frequency of the periodic signal for the giant flare data set of SGR  1806−20. QPO frequencies already detected by averaged power spectrum analysis and also with other mission RHESSI (Israel et al. 2005; Watts & Strohmayer 2006) are marked as small lines at the top axis. Those QPO frequencies are also detected by us. In addition, we have detected several more QPO frequencies (21, 59, and 116 Hz) with the Bayesian method, which were also predicted by Colaiuda et al. (2009).