Little is known about the epidemiology of Aichi virus, which is a new member of the family Picornaviridae, in the genus Kobuvirus. We report here on seroprevalence in France. Sera were screened using an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G. Of 972 sera tested, seroprevalence ranged from 25% for the 7-month-to-9-year-old age group to about 85% for the 30-to-39-year-old age group and older age groups. Our ELISA correlated well with the microneutralization technique. This study shows that Aichi virus is quite frequent in France and that seroconversion occurs before the age of 40.