Several glaciated valleys in the Northern Japanese Alps were filled up with outwash in each glacial stale (Fukai, 1960; Koaze et al., 1974; Shiki, 1974; Ito, 1982b, 1983). Many accumulation terraces develop along other nonglaciated valleys in such a high mountain area. Based on a tephrochronological study, Machida (1979b, 1980) indicates the possibility that deposits forming the accumulation terraces were supplied in each glacial stale. It is considered that these deposits were produced on mountain slopes by periglacial processes and due to the recession of timber line (Washburn, 1973; French, 1976; Ono and Masaki, 1980). Using a tephrochronological method, this study aims to examine (1) the distribution of accumulation terraces located along the River Chigawa, on the eastern part of Mt. Gakidake (2, 647.2m) in the Northern Japanese Alps (Fig. 1), and (2) the ages of debris supply during the late Pleistocene. Five terraces develop along the middle to downstream of the Chigawa ; they are classi-fied into Terraces I to V in this paper (Figs. 3 and 4). Except for Terrace I, others are accumulation terraces. Terraces II and III seem to have been formed under periglacial conditions, judging from the much amount of frost shattered debris involved in the terrace deposits. The timber line probably falled down at lower altitude (about 1, 000m) during the supply of these terrace deposits. The pumice fall deposit, DPm (Tateyama Volcano), covers the gravel layer of Terrace II (Fig. 2). The pumice fall deposits, EPm (Tateyama Volcano) and DKP (Daisen Volcano), cover the gravel bed of Terrace III, or are intercalated into this bed (Fig. 2). In view of the presumed age of DPm fall, a stage of accumulation terracing (Terrace II) in this area should be once of the cold periods before 100, 000 years B. P.. After the stage, a periglacial environment seems to have governed this area during the period between 70, 000 and 40, 000 years B. P., on the basis of the presumed age of the EPm and DKP. These two periods of debris supply correspond to the glacial stades where have been proposed in other high mountain area of the Northern Japanese Alps (Fig. 6).