This paper provides data-based analyses of recent interregional migration considering the examples of Japan and Poland. The analyses are conducted against the background of the general demographic and economic situations of both countries, in particular, regional disparities and economic growth. They aim at describing migrants’ behavior in Japan and Poland through a model consistent with the New Economic Geography (NEG) theory. Inspired by the model originally proposed by, the study constructs a migration model coherent with the NEG framework and tests the behavioral hypothesis. Interestingly, in both Japan and Poland, migrant behavior is responsive to stimuli stemming from the two following mechanisms: the relationship between the level of income inequalities and net migration toward capital regions; and similarly, the relationship between income inequalities movement and gross domestic product growth rate.