An analysis of the structure of Japanese home cooking was made by producing a correlation diagram of the ingredients from a large number of recipes on an Internet site. The structural analysis of the ingredients to construct the ingredient correlation diagram consists of a four-step process: 1) making a synonym dictionary, 2) sorting according to the frequency of use, 3) clustering by using a Kohonen network, and 4) linking the clusters by using an association rule. The stability and changeability of the diagram were considered. In respect of the stability, the constancy of the ingredients with time and their versatility across different recipes were confirmed. Changeability was investigated by monitoring the emergence of new elements in Japanese home cooking due to the fusion of Japanese, Western and Chinese cooking culture.