Several studies have examined how the associations of built environment attributes with walking behaviors may be moderated by socioeconomic status (SES). Such understanding is important to address socioeconomic inequalities in health through urban design initiatives. However, to date, there is no study examining the moderation effects of SES in the relationships of environmental attributes and walking in non-Western countries. The current study aims to examine associations of environmental attributes with walking behaviors among Japanese adults, and to test whether these associations were moderated by area-level SES. Data on walking were collected from Japanese adults using a nationwide Internet survey (N = 4605). Built environment measures including population density, street density, distance to the nearest public open space, and distance to the nearest commercial destination were calculated using geographic information systems software. An index of neighborhood deprivation was used as an area-level indicator of SES. Logistic regression models adjusted for clustering and sociodemographic variables were used. It was found that more residents in high SES areas walked for commuting, for errands, and for exercise compared with those who lived in low SES areas. When the whole sample was examined, all environmental attributes were associated with walking behaviors (except for street density not being associated with walking for exercise). Associations of environmental attributes with walking behaviors were moderated by area-level SES only in walking for exercise. Walking for exercise was associated with higher population density, higher street density (marginally significant), and shorter distance to the nearest commercial destination only in high SES areas. Our findings showed that the associations of these environmental attributes and walking behaviors were largely consistent across different SES levels. Therefore, urban design interventions focusing on low SES areas may help to reduce socioeconomic disparities in walking.