To improve the joining range of ultra high strength steel and aluminum alloy sheets in self-pierce riveting, the determination of die shape was proposed. A self-pierce rivet is driven through the upper sheet and flared in the lower sheet with a die, and the rivet directly pierces into the sheets without drilling the sheets beforehand unlike conventional rivets. Insufficient driving though the upper sheet and fracture of the lower sheet occur owing to the high strength and low ductility of the ultra sheet, respectively. To prevent the occurrence of defects, the determination of a die shape for the depth of die projection and the depth of the die was proposed. The ultra high strength steel sheet having a tensile strength of 980MPa and an aluminum alloy sheet were successfully joined using a die with appropriate shapes.