A protective mask includes a main frame body made of magnesium alloy and having an imaginary vertical central line. The main frame body has a plurality of first rods arranged along the central line, a plurality of second rods, and at least one first protrusion. Each of the first rods has spaced-apart first front and rear surfaces, and two opposite first connecting surfaces interconnecting the first front and rear surfaces. A thickness between the first front and rear surfaces is larger than a thickness between the first connecting surfaces. Each of the second rods is connected between two adjacent ones of the first rods. The first protrusion protrudes from the first front surface of one of the first rods.