Vibrational spectra of lactose molecule in the solid-state have been reproduced in the 4000-50 cm-1. The modified Urey Bradley Shimanouchi force field (mUBSFF) has been employed combined with an intermolecular potential energy function that includes Van der Waals interactions, electrostatic terms and an explicit hydrogen bond function. The force constants established previously for α-D-glucopyranose and β-D-galactopyranose as well as the crystallographic data of α-D-lactose monohydrate were the starting parameters for the present work. Satisfying calculated frequencies with suitable assignments have been obtained. Good agreements have been found between our results and those of vibration spectra of other disaccharides and monosaccharides.