Isotope ratio analysis of individual plutonium and uranium-plutonium mixed oxide (MOX) particles was performed using a combination of single particle transfer and thermal ionization mass spectrometry (TIMS) with a continuous heating method, namely the particles were measured without any chemical treatment. Accurate values were obtained for all isotope ratios of the individual particles prepared from standard solution. As a consequence, it is confirmed that the combination method is useful for isotope ratio analysis of individual plutonium and MOX particles.