A graphical Gaussian modeling method capable of speedily and accurately estimating a genetic network from an expression profile and an apparatus therefore are provided. The present invention provides a graphical Gaussian modeling method for estimating a genetic network including the steps of (a) clustering genes based on an expression profile, (b) selecting genes having a profile closest to a mean value of an expression profile per cluster to be used as representative genes representing the cluster, (c) obtaining a correlation coefficient matrix among representative genes, (d) obtaining a partial correlation coefficient matrix from the correlation coefficient matrix, (e) contracting the partial correlation coefficient matrix according to predetermined conditions and (f) displaying a contracted model based on the contracted partial correlation coefficient matrix.