Photoluminescence of Tb(III) complexes was studied as a function of temps. at 80-280 K for [Tb(bfa)3(H2O)2] (bfa: 4,4,4-trifluoro-1-phenyl-1,3-butanedionato), [Tb(hfa)3(H2O)3] (hfa: hexafluoroacetylacetonato), [Tb(tfa)3(H2O)2] (tfa: trifluoroacetylacetonato), [Tb(acac)3(H2O)3] (acac: acetylacetonato), and [Tb(hfa)3(tppo)2] (tppo: OPPh3). These complexes were classified into the 2 groups with different temp.-dependences. The 1st group consisting of [Tb(bfa)3(H2O)2], [Tb(tfa)3(H2O)2], and [Tb(acac)3(H2O)3] showed a dependence detd. by the energy gap between the excited triplet state of the ligand and the emitting level of Tb(III) ion. But for [Tb(hfa)3(H2O)3] and [Tb(hfa)3(tppo)2] contg. hfa as a ligand, not only the energy gap but also the energy barriers of the Forward energy transfer from the ligand to Tb(III) ion and Back energy transfer from Tb(III) ion to the ligand were taken into account for understanding their dependences. These results are discussed based on the reorientation of the complexes accompanied by the forward and back energy transfer processes using DFT calcns.