Application of “flame retardant magnesium (Mg) alloy”, which is defined as Mg-Al alloy with 0.5-2.0mass%Ca, is an effective way to improve flame retardance. In Japan, the national project of “Innovative Structural Materials R&D” has been launched since 2013FY. In the project, flame-retardant Mg wrought alloys for their allocation to high-speed railway bodies have been conducted. In the first half of the project, wrought Mg-Al-Ca alloys corresponding to A6005C (Al-Mg-Si) and A7204 (Al-Zn-Mg) alloys have been developed, where AX41 (Mg-4%Al-1%Ca (mass%)) alloy with superior extrudability corresponding to A6005C alloy, AX92 (Mg-9%Al-2%Ca) and AX81 (Mg-8%Al-1%Ca) alloys with good balance in mechanical properties corresponding to A7204 alloy, have been developed. After the development of the new alloys, as a next step, a prototype, which imitates railway vehicle body with 1/1 scale cross-section, has been produced with the purpose of verifying their assembling ability, forming ability, joining ability, cutting ability, surface treatment ability.