Galaxies grow through the cycle of gas accretion, star formation and outflow. Thus, quantifying gas flows is important to understand how galaxies evolve, especially around the epoch of the cosmic noon. Because metallicity is a tracer of star formation and gas flows, the comparison between observational data and chemical evolution model enables us to derive the rates of gas accretion and outflow for individual galaxies. In this talk, we focus on star-forming main-sequence galaxies at redshift 1.4 and discuss how well the rates can be constrained if we obtain precise data.