In order to investigate the change of enzyme activities during the fermentation of tobacco leaves, whole and cut leaves were treated for twenty days at 30℃ and 39℃ by the normal procedure and inoculation of yeast, respectively, and the activity of several enzymes was measured at proper intervals. 1) Alpha-amylase activity was steadily decreased with the progress of fermentation. 2) Invertase and catalase activities were steadily decreased until the mid of the period, and then increased again toward the end of the fermentation. The latter enzyme activity showed more marked change than the former. 3) Most of the polyphenol oxidase activity were decreased abruptly in the early stage of the fermentation, and thereafter leveled down slowly. 4) Peroxidase activity was detected throughout the fermentation but no remarkable change way observed. 5) Protease activity was not detected through the fermentation period.