  We investigate possible precursory phenomena of color superconductivity at
finite temperature $T$ with an effective theory of QCD. It is found that the
fluctuation of the diquark pair field exists with a prominent strength even
well above the critical temperature $T_c$. We show that such a fluctuaiton
forms a collective mode, the corresponding pole of which approaches the origin
as $T$ is lowered to $T_c$ in the complex energy plane. We discuss the possible
relevance of the precursor to the observables to be detected in heavy-ion
collisions.
