We investigated the effects of the application of chemical flower and fruit thinners on the fruit thinning time and fruit weight in four major apple cultivars. The effects of chemical flower and fruit thinning varied among cultivars due to the differences in the fruit drop rate of apical buds and the fruit set rate of axillary buds. In ‘Tsugaru’ and ‘Jonagold’, the single application of the flower thinner did not result in a labor-saving effect because the fruit set rate of axillary buds was high. Considering fruit enlargement, the combined application of the flower thinner and fruit thinner was the most effective in these two cultivars. In ‘Shinano Sweet’, the application of the flower thinner had no labor-saving effect on fruit thinning, but promoted fruit enlargement. In ‘Fuji’, the combined application of the flower and fruit thinners after hand pollination was the most effective for both labor-saving and fruit enlargement. The single application of the flower thinner had a more labor-saving effect than the fruit thinner.