We investigate vapor-liquid equilibria (VLE) for polymer/solvent systems using the same model binary parameters obtained from liquid-liquid equilibria (LLE) calculations. For the systems affected by free-volume differences between molecules, the VLE calculation results are corrected by Elbro et al.'s conceptual expression. In addition, we present the semi-quantitative description of contribution to VLE by oriented interaction. Our proposed model is directly applicable to VLE of binary polymer solution systems for various temperature ranges as well as for LLE calculations.