Objective: We aimed to quantify the personal economic burden of dementia care in Japan according to residence type.; Methods: A cross-sectional online survey was conducted on 3841 caregivers of people with dementia. An opportunity cost approach was used to calculate informal care costs. All costs and the observed/expected (OE) ratio of costs were adjusted using patient sex, age, and care-needs levels, and compared among the residence types.; Results: The mean daily informal care time was 8.2 hours, and the mean monthly informal care costs for community-dwelling people with dementia were US$1559. The OE ratio for informal care costs in community-dwelling patients was higher than in institutionalized patients.; Conclusion: The inclusion of informal care costs reduced the differences in total personal costs among the residence types. The economic burden of informal care should be considered when quantifying dementia care costs.