In Japan, even though sloped area is much larger than plain area, plain area is used for public facilities and industrial sites preferentially, and consequently, there are a lot of sloped urban districts which are commonly for residential use. Generally in sloped urban districts, there are various inconveniences for living due to the physical characteristics, such as insufficient road networks and many steep hillsides/stairs, so these inconveniences are viewed as the key elements inducing some problems such as depopulation and increased number of vacant house/lot at such districts. Therefore, in this study, the problem related to vacant house and lot is focused as the subject to solve among various kinds of problems emerging at sloped urban districts, and Nagasaki city is chosen as the targeted city to conduct a series of researches.<br> In the first half of this study, through a statistical analysis on the relationships between the emergence of vacant house/lot and physical residential environment which were investigated based on an on-the-spot survey, some significant environmental factors were clarified. Then, in the last half of this study, utilizing the concept of walking energy expenditure, accessibility from each residential site to daily facility were digitized in order to quantitatively detect and assess the relationship between the emergence of vacant house/lot and the walking energy expenditure.<br> The results obtained through this study can be concluded as follows: (1) It was difficult to renew or convert buildings and lands due to the legal responsibility of having a building site join the frontal road in sloped urban districts which comparatively has small number of roads in the past; however it has now become easy to do so even in sloped urban districts since designated streets have been implemented. Consequently, “join-the-frontal-road” issue is no more one of the influential factors to the vacant house/lot emergence. On the other hand, the car access-related factors such as the presence of garages and the width of frontal roads show significant impact on preventing houses and lots from being vacant. (2) For the residents whose main travel mean is walking, accessibility to out-of-house facilities is highly important, and the walking energy expenditure which is utilized as an index to evaluate the accessibility has statistically significant effects on the emergence of vacant houses and lots. Specifically, the distribution rate of vacant houses and lots is low in the districts which show high accessibility to educational facilities (e.g. kindergartens and elementary schools) and the place where residents can take public transportation. (3) Dissimilarly to general urban planning for plain sites which have few slopes and undulation, not only distance to walk but also undulation of routes significantly influence the energy consumption when it comes to sloped urban districts, and so the undulation of routes is needed to be involved in the calculation of accessibility.<br> Considering the results above, for the further progress of solution toward the issues related vacant houses/lots in sloped urban districts, the necessity to evaluate accessibility utilizing the concept of walking energy expenditure is highlighted. Also, it is implied that there is a clear need to construct road networks and conduct locational induction of facilities based on the result of such evaluation on walking energy expenditure.