Thermal equilibrium voltage generated in metal/insulator/metal (MIM) structure with polyimide Langmuir-Blodgett (LB) films is reported. That is, the open circuit voltage of the structures in thermal equilibrium was about 0.1V where the voltage was measured after separating the structures from the circuit for 20-40hrs. The voltage generation in the MIM structures seems to depend on such a thermal equilibrium voltage which is a very important keytoinvestigate the voltage generation in MIM structures.