A taxonomic study of the genus Maladera Mulsant of Korean Sericinae (Coleoptera, Melolonthidae) is presented. As a result, sixteen species are recognized including one new species, Maladera coreana sp. nov., and one subspecies, Maladera castanea koreana subsp. nov. A key, descriptions of the new species and subspecies, and photographs of aedeagus are provided.