We apply the chemical potential equalization (CPE) method to the calculation of the optical spectra in liquid methanol at 298 K and normal pressure. The configurations of the liquid are obtained by conventional molecular dynamics (MD) using a completely flexible all-atoms model. The infrared and Raman spectra are computed a posteriori using a CPE parametrization of methanol calibrated to reproduce the electronic properties of the isolated molecule evaluated with accurate ab initio calculations. The MD/CPE method reproduces correctly the optical spectra in the region of the intermolecular motions. The spectra are discussed and interpreted on the basis of hydrogen bonding structure and dynamics.