[Problems] It is an object of the invention to provide a producing method of a magnesium-based alloy screw capable of producing a screw made of magnesium-based alloy having excellent strength with excellent productivity, and to provide a magnesium-based alloy screw. [Means to Solve the Problem] The producing method includes a head forging step in which a head working for forming a head portion of a screw on a wire made of magnesium-based alloy obtained by drawing is carried out by warm working to produce a screw blank, and a thread rolling step in which thread rolling for forming screw thread on the screw blank is carried out by warm working to produce a screw. The head working in the head forging step is carried out using holding die which fixes the wire and a punch which forms a head portion of the screw. The holding die and the punch are heated, in which at least the holding die are heated to 140° C. or higher and 250° C. or lower, thereby heating the wire to 140° C. or higher and lower than 250° C.