We confirm the usefulness of the newly-proposed method, EW(Hbeta)-Beta method, which enables us to find Lyman continuum galaxies with high escape fraction of LyC photons independent of the IGM absorption. EW(Hbeta)-Beta method is proposed by Zackrisson et al.(2013), and the method uses the equivalent width of Hbeta and UV spectral slope beta. We observe candidates of Lyman Continuum Galaxies at z~3 with Keck/MOSFIRE for measuring the Hbeta emission line flux. As a result, we find that the escape fraction of LyC expected from the EW(beta)-Beta method is consistent with that estimated from the direct LyC measurement.