Electromigration characteristics of eutectic SnPb solder were studied using thin stripe-type test structures. Significant changes in the microstructure were observed after electromigration test, in which the temperature and the current density were varied from 80 to 100 $^{circ}C$ and from 4.6${ imes}$10$^4$A/$ extrm{cm}^2$ to 8.7${ imes}$10$^4$A/$ extrm{cm}^2$. While voids or local thinning were found near the cathode end, hillocks were mainly observed near the anode end. From resistance measurements, it was calculated that the activation energy of the eutectic SnPb solder for electromigration was 0.77 eV. The dominant migrating element along the electron flow at 100$^{circ}C$ was Pb.