This study was carried out to investigate working time, productivity, and heart rate during thinning using chain saw in Japanese larch(Larix leptolepis) plantation site for analysis of physical work load, and to investigate maximal oxygen uptake of worker for analysis of maximal work capacity. The real working time was 366 minutes in a day ; about 192 minutes in the a.m., 174 minutes in the p.m.. The ratio of real working time per total working time was approximately 90%. The rate of moving(Mo) to real working times was 26.3, which was the largest one of work elements. Average maximal oxygen uptake, as an asset of personnel performance, was 2.42ℓ/min(46.5㎖/㎏/ min) . During the real working time, average productivity, the mean rate of increase of heart rate, and the mean work load index was 2.62㎥/hr, 93.2%, and 41.9%, respectively.