1. A probability density function separating apparatus that separates a predetermined component in a given probability density function, comprising: a domain transforming section that is supplied with the probability density function and transforms the probability density function into a spectrum in a frequency domain; and a deterministic component computing section that multiplies a multiplier coefficient according to a type of distribution of a deterministic component included in the given probability density function by a first null frequency of the spectrum in the frequency domain and computes a peak to peak value of the probability density function with the deterministic component.