  We study the properties of the 0++ glueball at finite temperature using SU(3)
quenched lattice QCD. We find a significant thermal effects near T_c. We
perform the \chi^2 fit analyses adopting two Ansaetze for the spectral
function, i.e., the conventional narrow-peak Ansatz and an advanced
Breit-Wigner Ansatz. The latter is an extension of the former, taking account
of the appearance of the thermal width at T>0. We also perform the MEM
analysis. These analyses indicate that the thermal effect on the glueball is a
significant thermal-width broadening \Gamma(T_c) \sim 300 MeV together with a
modest reduction in the peak center \Delta\omega_0(T_c) \sim 100 MeV.
