The author investigated the river terraces along the Saru river, Hokkaido, Japan. First, he divided the Quarternary age into four stages by means of the age of marker tephra layers, such as Spfa-1 (ca. 33, 000 yrs. B. P.), En-a (ca. 15, 000yrs. B. P.), Ta-d (ca. 9, 000yrs. B. P.) and Ta-d (ca. 550 yrs. B. P.) which were named Ms, Mw-I, Mw-II, and F stages in the descending order (Fig. 1). Secondly, the river terraces were classified into four topographic surfaces based on topographic continuties, which were named I, II, III, and IV surfaces in the ascending order. Comparing M_??_F stages with I_??_IV topographic surfaces, respectively, he found that there was a time lag within the formation of each topographically continuous terrace surface (Figs. 4 and 5). One case of time lag is shown by the convergence of terraces, (e. g., II_??_IV surfaces converge into one surface in the middle course; the lag of which is estimated 2_??_4×104 yrs). The other is attributed to the translocation of downcutting place of river bed (e. g., I surface is considered to have formed whithin a time of about 1×104 yrs.). I and II surfaces along the lower course were formed in the Postglacial age. While, III and IV surfaces were formed by the translocation of knick-point, accompanied with the lowering of sea level during the Lastglacial age. Judging from the field evidences and longitudinal profiles (Figs. 4 and 5), down-cutting of II surface was initiated from the middle course, slowly proceeding to upward and downward. It is supposed that this phenomenon was caused by the complex influence of the following factors: (1) increasing of curvature in river profile, probably effected by the relative decrease of fluvial load and sea level rise in the Postglacial age, (2) slight falling of sea level after the maximum phase of Jomon transgression, (3) other unknown factors. The river traces distributed along the course of the Saru have been formed as a result of successive translocation of down-cutting, lateral erosion, and depositional areas to upward and downward along the river course. Fig. 7 shows the presumed changes of river bed altitudes since Lastglacial time along the Saru.