Enterovirus focal encephalitis is a rare clinical entity that is characterized by focal neurological signs including seizure, hemiparesis, hemichorea, and headache, which are mainly followed by rapid spontaneous improvement. We herein describe the case of a 9-month-old boy who developed Coxsackie virus B5 (CVB5) focal encephalitis with seizure clusters in the eruption stage of roseola infantum-like illness, which were followed by rapid improvement and benign outcome. Lumbar puncture indicated pleocytosis, and CVB5 infection in the cerebrospinal fluid was subsequently identified on genome sequencing and virus isolation. Magnetic resonance imaging and electroencephalography showed no abnormal findings at the acute stage or on 2 month follow up. Although the pathogenesis of enterovirus focal encephalitis currently remains unclear, the pure synchronism of seizure cluster and eruption in this case suggests the involvement of local vascular impairment as the underlying pathogenesis.