Japan is facing serious social problems in the guise of rapidly increasing medical costs for the elderly and regional gaps of medical costs among prefectures, resulting from an aging society with a low birth rate. This study examined the relationship between care-related factors and medical costs in all 47 prefectures. Eighteen indices were examined as care-related factore in the elderly themselves, at their homes, and in their communities. The medical cost for inpatients was used as an index of medical costs for the elderly because the highest correlation was observed in this group Nine indices were selected as care-related factors by correlation analysis. To clarify what indices are associated with medical costs for inpatients, stepwise multiple regression analysis was performed using these nine indices. Three indices accounted for 67.8% of the correlation of medical costs for inpatients and the percentage of aged people who lost their spouses (women aged more than 60) had the strongest positive correlations, while percentage of people who had their own houses had the strongest negative correlations with medical cost for inpatients.