An (N+2)-field model proposed in our previous study (Shimada and Tomyama, 2005) was modified for application to compressible bubbly flows with chemisorption by taking into account the dependence of phase densities on components. Then, a numerical method for solving the modified (N+2)-field model was developed. The proposed method was verified through a sample calculation. i.e., a simulation of a bubbly flow with chemisorption in a rectangular vessel. Predictictions were compared with experiments. As a result, it was confirmed that the proposed method gave good predictions for the time evolutions of pH and gas holdup and for natural convection induced by the heat of reaction.