To provide a new coating method for magnesium or a magnesium alloy formed product by which a protective film can quickly be deposited on the surface of the formed product at a low cost.

After forming the formed product 20 by using forming dies 11, 12, the forming dies 11, 12 are opened and a resin film 30 is disposed between the forming dies 11, 12 and the formed product 20. Successively, the forming dies 11, 12 are closed and the resin film 30 is held between the forming dies 11, 12 and the formed product 20, and melted on the formed product 20 with the remaining heat of the formed product 20. In this way, the coating is easily and quickly deposited and therefore, the bringing about of surface blister or of deformation of the formed product can be avoided. Further, the coating is obtained at a low cost.