We discovered the unusually gigantic boulders of granite from the Yamanakano and Tsuchitori areas of Kui Town in Mitsugi County，Hiroshima Prefecture，western Japan. The areas studied by us are situated in the southern part of the so-called Sera highland regarded as the elevated peneplain and consist of the Holocene deposits and the granite intruded in the Late Cretaceous time. The gigantic boulders can be classified into two types of boulders such as type A and type B. In this paper are given the description of the boulders and the discussion on the origin of the gigantic boulders of type A and type B.