With urbanization, the amount of electric-power consumption and its ratio to the total energy consumption have increased. Due to this increase, a possible power outage will have a severe impact to the affected urban area. In this study, we propose a quantitative evaluation method of the power outage effects. Power outage is defined as “a situation, in which people cannot do their usual activities” and a power outage effect index is evaluated as a total value of disturbance of various human activities. Proposed method is applied to Tokyo Metropolis and power load characteristics are analyzed. Prepared are maps of the power outage effects for each substation area.