Intracellular Ca2+ signal controls various cell functions such as gene expression, cell death, proliferation, and migration. In immune cells, the activation of K+ channels promotes Ca2+ entry and therefore regulates cell functions. Inwardly rectifying K+ (Kir) channels play important roles in the formation of resting membrane potential in various types of cells. Kir2.1 channel is expressed in macrophages, however, the contribution of Kir2.1 channels to the pathophysiological functions is unclear. In this study, we examined the pathophysiological roles of Kir2.1 channels in murine bone marrow-derived macrophage (BMDM). The resting membrane potential in BMDM significantly depolarized by 100 μM Ba2+ (a Kir blocker). The resting [Ca2+]i and store-operated Ca2+ entry (SOCE) induced by 1 μM thapsigargin were significantly reduced by 100 μM Ba2+. Neither application of Ba2+ nor ML133 (a Kir2 selective blocker) affected differentiation of myeloid progenitor cell into BMDM, phagocytosis, and proliferation. On the other hand, migration of BMDM was significantly inhibited by these Kir2.1 inhibitors. These results suggest that the activity of Kir2.1 channels regulates resting membrane potential and [Ca2+]i, and thus promotes migration to inflammatory regions in macrophage.