  We study the low-lying scalar mesons of light u, d, s flavors in the QCD sum
rule. Having all possible combinations of tetraquark currents in the local
form, QCD sum rule analysis has been carefully performed. We found that using
the appropriate tetraquark currents, the masses of sigma, kappa, f_0 and a_0
mesons appear in the region of 0.6 -- 1 GeV with the expected ordering. The
results are compared with that of the conventional \bar{q} q currents, where
the masses are considerably larger.
