Normal cardiomyocytes are highly dependent on the functional expression of ion channels to form action potentials and electrical coupling with other cells. To fully determine the scientific and therapeutic potential of stem cells for cardiovascular-disease treatment, it is necessary to assess comprehensively the regulation of stem-cell electrical properties during stem cell-cardiomyocyte interaction. It has been reported in the literature that contact with native cardiomyocytes induced and regulated stem-cell cardiogenic differentiation. However, in conventional cell-culture models, the importance of cell-cell contact for stem-cell functional coupling with cardiomyocytes has not been elucidated due to insufficient control of the cell-contact mode of individual cells. Using microfabrication and laser-guided cell micropatterning techniques, we created two biochips with contact-promotive and -preventive microenvironments to systematically study the effect of contact on cardiogenic regulation of stem-cell electrical properties. In contact-promotive biochips, connexin 43 expression was upregulated and relocated to the junction area between one stem cell and one cardiomyocyte. Only stem cells in contact with cardiomyocytes were induced by adjacent cardiomyocytes to acquire electrophysiological properties for action-potential formation similar to that of a cardiomyocyte.