Abstract: The high-strength non-combustible magnesium alloy is obtained by adding at least one supplementary additive selected from among carbon (C), molybdenum (Mo), niobium (Nb), silicon (Si), tungsten (W), alumina (Al2O3), magnesium silicide (Mg2Si) and silicon carbide (SiC) to small chip-like blocks of a non-combustible magnesium alloy resulting from adding 0.5 to 5.0% by mass of calcium to a magnesium alloy to produce a crushed product, and subjecting the same to forming, sintering and plastic working. The high-strength non-combustible magnesium alloy exhibits excellent joining ability, and can therefore enhance weldability when used in a filler metal.