⁵⁷Fe-Mössbauer studies on local and network-structure of several oxide glasses are summarized. The iron (Fe³⁺) is substituted for individual NWF (network former): i.e., V⁵⁺, Ti⁴⁺, Te⁴⁺ AI³⁺, Ga³⁺, and B³⁺. A linear relationship was discovered for several oxide glasses between Tg (glass transition temperature) and Δ (quadrupole splitting) of Fe³⁺, being expressed by Tg = aΔ + b. The discovery of “Tg-Δrule” suggests that structural information obtained from Fe³⁺ is reflected in the physical properties of the whole glass matrix. The rule indicates that Tg of oxide glasses is proportional to the local distortion or asymmetry of NWF-oxygen polyhedra.  The “Tg-Δrule” is also valid in the case of γ -ray irradiated glasses and glass-ceramics. The ⁵⁷Fe- and ¹¹⁹Sn-Mössbauer spectroscopy was furthermore utilized for the study of local structure and Cu-site vibration of superconducting YBa₂Cu₃O_7–y and Bi(Pb)₂ Sr₂Ca₂Cu₃Sn_0.015O_10–y. Softening (quenching) of Cu(1)- and Cu(2)- site vibration was observed around the Tc(on)of superconducting transition in the former, whereas the latter showed “normal” vibrational mode expressed by combined Debye and Einstein model.  This suggests that softening of Cu(2)- and Cu(1)- site vibration cause or result in the superconducting transition.