Use of natural redioactive tracers for the estimation of sources and direction of sand drift was examined for the case if the Sendai Coast. Sand samples were taken along the coast, washed with fresh water, dried, and sieved mechanically. Heavy minerals in these samples were separated with liquid of tetra-bromo-ethane of which specific gravity is 2.95. The content of thorium in heavy minerals was analyzed on the basis of radioactive equilibrium of thorium decay chain by measuring the intensity of gammna-rays emitted from Pb-212 (0.239 MeV). The concentration of thorium in heavy minerals and concentration of thorium in sands including heavy minerals were calculated with the result of the gamma-ray analysis. According to the usual sedimentary analysis and statistical analysis of predominant direction of waves, it was possible to consider that the predominant direction of sand drift along the Sendai Coast north of the Abukuma River in toward the north. The concentration of thorium is sands showed distinctly the tendency to decrease gradually in the direction of sand drift, while that in heavy minerals showed the tendency to increase in the same direction. Finally, it was concluded that the concentration of thorium in sands is preferrable as an index for the estimation of predominant direction of sand drift on the basis of the sorting process of sands by waves.