Trace elements of sea cabbage (Kombu) produced in Japan and China were analyzed by an XRF spectrometer with three-dimensional polarization optics. Fourteen elements (S, Cl, K, Ca, Mn, Fe, Cu, Zn, As, Br, Rb, Sr, I, Ba) were detected in all kelp samples (88 samples from China and 25 samples from Japan). The optimum measurement conditions for XRF resulted in a sub-ppm level analysis for heavy elements such as Ba (0.60 ppm as detection limit). Nine elements of K, Mn, Fe, Cu, Zn, As, Br, Rb, Sr were determined using calibration curves obtained from the 14 certified reference materials. The concentration of iodine was also easily determined using calibration curve obtained from self-produced standard samples. The concentrations for iron, zinc, and iodine were varied among the kelp samples produced in difference region.