This paper was concerned with “the vulgarity of the masses” that is regarded as a mental disposition of an individual, which might be of relevance to the issue of consensus building and public acceptance in an infrastructure planning process.Based upon Ortega's Political Philosophy, it was hypothesized that if people bacame vulgar, social consensus around public works would become difficult to be achieved, even if government's policy did not change at all. In order to test this hypothesis, we implemented a questionnaire survey. The obtained data statistically supported the hypothesis, and it was indicated that the masses might disturb consensus building for public works.