An evaluation section identifies, in a list of candidate compounds, a group of candidate compounds having the degree of reverse similarity greater than or equal to a threshold s1. When all candidates in the group of candidate compounds have differences between the degrees of similarity that are greater than or equal to a threshold s2, the evaluation section judges that there is a composite state. The difference between the degrees of similarity is computed by subtracting the degree of forward similarity from the degree of reverse similarity. The similarity ratio may be used in place of the difference between the degrees of similarity.