Abstract: A suitcase includes a main body and a retractable handle assembly mounted on the main body. The handle assembly includes two outer pipes and at least two inner pipes retractably mounted in the outer pipes respectively. Each of the inner pipes and the outer pipes of the handle assembly is made of a plastic pipe which is formed by a primary material and an auxiliary material. The primary material and the auxiliary material are initially mixed and fused, and are then extruded and molded to form the plastic pipe of each of the inner pipes and the outer pipes of the handle assembly. The primary material includes polycarbonate (PC) or polyoxymethylene (POM). The auxiliary material includes fiber. The fiber of the auxiliary material includes glass fiber or carbon fiber.