Turbopump is typically an assembly of rotors and casings, and there are a number of joints between them. Every joint should be leak-proof, so there is always a seal to accomplish the goal. Among various seals, metal seals are advantageous in that they are robust at high pressure, and at wide range of temperature. In this study, flange joints using conical seal made of stainless steel, solid flat metal seal made of copper and metal C seal made of Inconel 718 were structurally designed and analyzed, considering both initial tightening and operating conditions.