This paper reported a case of onychomadesis which appeared on the nails after heal of cutaneous lesions of hand-foot-mouth disease (HFMD). There were a few reports describing onychomadesis after HFMD; however, the mechanism is still unclear. The present case was prospectively observed, and onychomadesis was found to develop only on the nails having cutaneous lesions of HFMD. We considered that nail dysfunction due to direct inflammation spreading from skin eruptions around nail is one of the causes of onychomadesis linked to HFMD.