In this paper, we propose a discord discovery method which finds the
-most dissimilar subgraphs of size
among the subgraphs of the same size of an input graph, where the values of
are given by the user. Our algorithm SD3 (Subgraph Discord Detector based on Dissimilarity) exploits a dynamic index structure and its effectiveness is demonstrated through experiments using graph data in chemical-informatics and bioinformatics.