The genus Carinaulus Tesař, belonging to the scarab beetle subfamily Aphodiinae, currently includes 20 valid species distributed across the Eastern Palearctic and Oriental Regions. The genus is characterised by the following elytral features: broad and deep striae; striae prominently punctate and distinctly crenulate; intervals tectiform with a median carina; and the sixth and eighth intervals joined at the pre-apical area, though lacking a carina in that region. Two species are recognised in the Korean Peninsula, Carinaulus inexpectatus (Balthasar, 1935) in North Korea and Carinaulus coreensis (Kim, 1986) in South Korea. Carinaulus inexpectatus (Balthasar, 1935), with Vladivostok designated as its type locality, occurs in the Russian Far East and North Korea, whereas C. coreensis (Kim, 1986) is considered endemic to South Korea. During examination of Korean Carinaulus Tesař, we compared several specimens of Carinaulus coreensis (Kim, 1986), including a paratype and C. inexpectatus (Balthasar, 1935) collected from North Korea. We found that the two nominal species cannot be distinguised by the morphological characters, including labrum chaetotaxy and male genitalia. Accordingly, it is proposed that Aphodius coreensis Kim, 1986, is a subjective junior synonym of Aphodius nexpectatus Balthasar, 1935.