The density of rockfill material heavily affects on the mechanical property because of non-cohesive material, but evaluation of in-situ density of rockfill material has been difficult issues due to large particle size. This paper studies compaction degree of rockfill material by the existing results of several in-situ rolling compaction tests, and density and confining pressure dependency of already tested strength data of rockfill material. Rockfill material of older dams were dumped, so the density was loose or medium dense. Crest settlements after embankment of dams, which are constructed after almost 1960, were greatly smaller because of heavy compaction roller. Investigated tests consist of large triaxial compression test, and most of Japanese strength tests are based on 30cm of diameter and Marsal, R.J. (1973) with 1130cm of diameter is contained. Rockfill material strength in Japan indicates higher than other countries especially in case of very dense density, and rockfill material strength consisting of shale and slate shows lower. Internal friction angle of rock material except shale and slate shows higher than 40° even with loose condition.