Intramolecular diamagnetic currents in neutral polyacetylene molecules with microscopic sizes, the mechanism of which has not been elucidated, can be explained by electron pairing originating from attractive Coulomb interactions between two electrons with opposite spins occupying the π molecular orbitals, mediated through nuclei with positive charge, in neutral polyacetylene molecules at 298 K, according to our calculated results. That is, vibronic interactions cannot play a role in electron pairing in the neutral polyacetylene molecule with microscopic size. The transition temperature Tc,Nchainπ value at which intramolecular diamagnetic currents can disappear in each polyacetylene molecule is estimated. The Tc,Nchainπ values for the neutral polyacetylene molecules with microscopic sizes are estimated to be much larger than the superconducting transition temperatures Tc,BCS values for the conventional superconductors with macroscopic sizes. This result can be understood from continuous energy levels of el...