The present invention pertains to a production method for a fire-resistant magnesium alloy having the mechanical characteristics of a long-period stacked magnesium alloy and having an ignition temperature of at least 800°C. The fire-resistant magnesium alloy production method dissolves a fire-resistant magnesium alloy containing a atom% of Zn, a total of b atom% of at least one type of element selected from a group comprising Gd, Tb, Tm, and Lu, and x atom% of Ca, with the remainder being Mg. a, b, and x fulfil formulas 1-4. Formula 1: 0.2 ≤ a ≤5.0. Formula 2: 0.5 ≤ b ≤ 5.0. Formula 3: 0.5a - 0.5 ≤ b. Formula 4: 0