The electronic structures of a high spin molecule, m-phenylenebis (phenylmethylene) (m-PBPM) ion are studied with a semi-empirical model for n and pi electrons using the unrestricted Hartree-Fock(UHF) and resonating Hartree-Fock(Res HF) approximations. The experimental results show that both the cation and anion have the quartet ground state. In the UHF approximation, the doped charge is always localized around a carbene as a spin density wave(SDW) polaron. The Res HF results show that the quartet state is more stabilized than the doublet state by about 0.1eV due to the quantum motion of the SDW polaron between the right and left carbenes. This is true even if the quantum fluctuations in phenylenes, the most significant energetically one are taken into account. The stabilization energy by the latter effect is about 2eV, that is, about three times as large as the ground state correlation energy in benzene.