In the present study, we summarized the results of Undaria pinnatifida seedling production using a new method by application of free-living gametophytes conducted at seedling production sites in Tokushima Prefecture from 2011 to 2019. Seedling production by application of free-living gametophytes was started at a production site by a fisherman in 2011. Subsequently, the number of production sites and fishermen has progressively increased, and 37 fishermen in 2019 worked on the new method at 28 production sites. In addition, the length of the applied seed strings was 450 m in 2011, but in 2019, it reached 35,820 m. The total length of applied seed strings we investigated from 2013 to 2019 was 53,735 m, of which 42,251 m (78.6 %) successfully produced seedlings and the results were stable at about 80 % every year. In contrast, the conventional seedling production using zoospores was not stable, ranging 0-60 % in the seven years, and was consistently less than the results of the new method every year. Seedling production of U. pinnatifida using free-living gametophytes has remained at an experimental scale for a long time, however now the seedling production method by application of free-living gametophytes has been completely realized to enable commercialization at the production sites.