A power device and a guard ring structure surrounding the power device are provided. The power device includes: a buried layer of a first conductivity type and a buried layer of a second conductivity type disposed within a substrate; a body region of the first conductivity type and a drift region of the second conductivity type disposed on the buried layer of the first conductivity type; and a gate electrode, a source electrode, and a drain electrode disposed on the body region of the first conductivity type and the drift region of the second conductivity type. The guard ring structure includes: a first guard ring of the second conductivity type adjacent to the power device; a second guard ring of the first conductivity type adjacent to the first guard ring; and a third guard ring of the second conductivity type adjacent to the second guard ring.