Flavor is one of the important factors for udon, white salted Japanese noodles. Using gas chromatography/mass spectrometry, we analyzed the volatile compounds from the flour, dough, and boiled noodles to clarify the mechanism of udon flavor formation. Hydrocarbons were the main compounds from the flour, while aldehydes and ketones were the main compounds from the dough and noodles. These aldehydes and ketones are presumed to be generated from the enzymatic oxidation of unsaturated fatty acids by lipoxygenase (LOX) upon the addition of water. LOX activity was significantly higher in the cultivar Norin61 than in Satonosora. In conclusion, the characteristic volatile compound profiles of Norin61 are due to differences in LOX activity. These results have been applied to the development of new value-added noodle products by various companies.