This study is one of the first ever to attempt to measure the extent of relative deprivation in Japan. Its aim is to establish a relative deprivation scale, closely following the methods developed by Townsend (1979) and others and taking into account differences between the cultures of the U.K. and Japan. Then, the study analyzes the relationship between relative deprivation and income poverty, and individual and household characteristics. The study uses two datasets from two nationally conducted surveys. One identified socially perceived necessities, as developed by Mack and Lansley (1985). The other established a relative deprivation scale using the necessities that were identified by the former. Applying the relative deprivation scale, this study revealed three major findings. First, under a certain threshold household income, the relative deprivation scale increases dramatically, as is the case in the United Kingdom and other countries. This threshold is around 4 to 5 million yen per year. Second, those whose lifestyle deviates from the social norm experience a higher risk of relative deprivation. In particular, single people in their 30s to 50s, people with members of their household who are ill, and single mothers exhibited high levels of relative deprivation. Third, young people are found to be at high risk of relative deprivation. The deprivation scale is highest for those in their 20s, relatively low for those in their 30s to 60s, and rises again for those in their 70s. Comparing elderly people (greater than 60 years old) with younger people (20 to 60 years old), both the prevalence and depth of deprivation was higher for the young, even for those in the same income range. It is too early to draw conclusions for public assistance or other social security systems from the results of this study. However, this study is an important first step in extending conventional poverty research which use only income or consumption data, toward understanding the complexity of poverty.