  We report the first study of the glueball properties at finite temperatures
below T_c using SU(3) anisotropic lattice QCD with beta=6.25, the renormalized
anisotropy xi \equiv a_s/a_t = 4 and 20^3 \times N_t
(N_t=35,36,37,38,40,43,45,50,72) at the quenched level. From the temporal
correlation analysis with the smearing method, about 20 % mass reduction is
observed for the lowest scalar glueball as m_G(T)=1250 \pm 50MeV for 0.8 T_c <
T < T_c in comparison with m_G \simeq 1500 \sim 1700MeV at T \simeq 0.
