This paper analyzes the sources of quality change in labor inputs in Japan for the period of 1960-1979. Decomposition of quality change was made using the Divisia indices of labor input, which are consistent with transcendental logarithmic aggregator functions. A comparison between Japan and the U.S. was made citing some U.S. results in a comparable framework. The empirical results show that quality changes in labor inputs in Japan were positive through 1960-1979, and that the sources of these quality changes were mainly an age effect, an education effect and the interactive effects of education-age and education-occupation. During this time, the Japanese economy was catching up with the technology of the U.S. and Western Europe. The results of this paper, concerning quality changes in labor inputs, are consistent with this catch-up process. That is, the more the technology level is enhanced through the development of technology, the more is the quality change in labor input required. This coincidence of quality change in labor with technological development has been one of causes of rapid productivity change in the Japanese economy. On the other hand, the comparison between the U.S. and Japan shows that quality change in labor input in the U.S. was apparently small compared to that of Japan, especially in terms of the sex and age effects. Only the education effect turned out to be significantly positive, though its impact was reduced when an adjustment for occupation was made. This result shows that quality changes in labor input have not been a major factor for the productivity change in the U.S., while they contributed significantly to Japanese productivity changes.