We explore the polytope structures for genuine entanglement, biseparability and full biseparability of multi-qubit GHZ diagonal states. We show that biseparable GHZ diagonal states make truncation polytopes, and fully biseparable states make the convex hulls of simplices and cubes. We also compute precise volumes for genuine entanglement, biseparability and full biseparability among all GHZ diagonal states. This talk is based on a joint paper with Kyung Hoon Han which will be posted soon under the same title.