Canine teeth of northern fur seals were analyzed by PIXE to examine relationship between trace elements in fetal teeth and those in mother's teeth. The trace elements including Mn , Fe , Zn and Sr were detected in all the sample. No significant difference was detected in the mean concentration of Mn between fetal teeth and mother's teeth. On the other hand, significant difference was detected in the mean concentration of Fe , Zn and Sr between the enamel tissue in fetal teeth and the enamel tissue in mother's teeth. Additionally, difference in the change of concentration was detected among elements: Fe concentration in enamel tissue has no relation to ages, Zn concentration in enamel tissue decreases with age and Sr concentration in enamel tissue increases with age. The fluctuation of trace elements is possibly affected by seal's migration route and / or the mechanism of the element transfer from maternal sera to fetus through the placenta.