PURPOSE: Premature mortality offers an alternative approach for monitoring the burden of mortality; however, little is known about its measures for stomach cancer. In the present study, we investigated temporal changes in premature mortality because of stomach cancer in the Japanese population from 1980 to 2015. METHODS: Mortality data for stomach cancer were obtained from the World Health Organization mortality database. Years of life lost (YLL) was calculated using Japanese life tables. The average lifespan shortened was calculated and defined as the ratio of YLL in relation to the expected lifespan. RESULTS: Over a 35-year time frame, the age-standardized rates adjusted to the World Standard Population for deaths from stomach cancer substantially decreased in both sexes. The results from the average YLL (AYLL) measure showed that lifespan of stomach cancer patients was prolonged by about 3 and 5 years in men and women, respectively. The average lifespan shortened measure showed that stomach cancer led to a loss of 18.5% of lifespan among men and of 21.9% among women in 1980, but these numbers were reduced to 13.6% and 14.5%, respectively, in 2015. CONCLUSIONS: Our study demonstrated decreasing trends in premature mortality for stomach cancer in Japan over a 35-year period.