Gluten free means not containing gluten that is found in flour, etc. Now, gluten-free diets are popular among people. Buckwheat itself is gluten free; however, soba is not completely gluten free. The reason is that in the process of making soba, wheat flour is added to stick the buckwheat together. It also helps the noodles go smoothly down your throat. There is soba made without wheat flour called “Towari (十割) soba (100% soba)” but it is dry and the noodle snaps easily. Moreover, wheat flour might be used when soba dough is kneaded. So it is difficult to say Towari soba is completely gluten free either.
In other words, If you prefer gluten free food just to get more healthy diet, “Towari (十割) soba (100% soba)” could be a good choice, however if you have a serious condition like celiac disease, you should be careful if wheat flour is also not used during soba kneading process.
Although soba is not completely gluten free in most cases, it is one of the healthiest foods you can eat. It will be nice to try and add different soba dishes to your diet!