We developed a method to measure the quantity of TTV-DNA. This measurement is based on the principle of the real time PCR method using the TaqMan probe. By measuring the change of the fluorescent intensity caused by FRET, we could detect the amount of TTV-DNA. This method has the characteristics that the possibility of the contamination is very rare when it is compared with the usual PCR method, because the reaction system contains UNG and dUTP. This quantification method is useful for the future research of TTV to study the relationship between this virus and diseases.