Here we report newly found alien herb in Japan, Moenchia erecta (L.) G., M. et Sch. (Caryophylla-ceae). The species is native to Europe and has been naturalized in Australia, Canada and United States. Since 2008, the species has been known its existence in Hyogo Prefecture, and also found from Mie Prefecture in 2014. Its small habit and short life cycle may prevent them find out from the other part of Japan, but the species may spread out throughout this country.