The method of producing a magnesium alloy joined part has the following steps: a joining step of joining a reinforcing material made of metal to a plate material made of magnesium alloy without allowing an organic material to remain at the joined portion and a plastic-working step of performing plastic working on the plate material to which the reinforcing material is joined. A desirable means of joining the reinforcing material to the plate material can be to use an inorganic adhesive. Because the magnesium alloy joined part is formed by a structure in which the reinforcing material is joined to the plate material, in comparison with the case where the reinforcing material is formed by machining or the like, the magnesium alloy structural member can be obtained with high production efficiency.