1. A computer-readable recording medium that stores therein a delay analyzing program making a computer execute: receiving a result of timing analysis of a target circuit; detecting, from paths in the target circuit, critical paths of which a delay value is within a predetermined range based on the result of the timing analysis; calculating an average delay distribution of paths other than the critical paths based on an average delay value of each of the critical paths; calculating a probability density distribution of the critical paths based on a probability density distribution of delay of each circuit element constituting the critical paths; calculating a probability density distribution of all of the paths based on the probability density distribution of the critical paths and the average delay distribution; and calculating difference between a statistical delay value of the critical paths and a statistical delay value of all of the paths based on the probability density distribution of the critical paths and the probability density distribution of all of the paths.