In-situ measurement of transmutation of Cs into Pr was performed, and the surface distribution of Pr was investigated using X-ray fluorescence spectrometry (XRF) at SPring-8, a large synchrotron X-ray facility. The in-situ measurement indicated that Pr emerged and Cs decreased at some points after D2 gas permeation, though any Pr cannot be observed before D 2 gas permeation at all the points on the Pd complex surface. Using small size X-ray beam in 100-and 500-μm2, we obtained two-dimensional XRF spectra for three permeated samples, from which we detected Pr. Pr was detected again by the two small X-ray beams as expected. The amount of Pr varied greatly at different locations of the Pd surface, however, a clear correlation between surface structures and distribution of Pr has not seen up to now. Experimental results suggest that nuclear transmutations do not occur uniformly but some uncertain factors, presumably condensed matter effects in the present Pd/D/CaO system, have a large effect on the rate or the process of the reactions.