Because one phenomenon of life is caused by a great variety of genes and molecules, understanding of one phenomenon of life needs exhaustive collection of gene expressions. The collection, called gene expression profile, is recently getting possibility by microarray, which is one of a method to investigate whether a gene is expressed or not. Data Mining, the field of computer science for discovery of useful summary of data, is in the spotlight as analysis method of the collected gene expressions. In this paper, we will introduce the techniques of Data Mining, and explain how you can apply the techniques to analysis of gene expression profiles.