The requirements to apply magnesium alloys for aerospace applications are focused, and the feasibility to construct aerospace structures using magnesium alloys is investigated. As the material properties of magnesium alloys have advantages of light weight, high specific stiffness, and high damping characteristics, they are supposed to be advantageous for designing light-weight aerospace structures. Additionally, as the magnesium alloys are easily recycled with low energy costs and without environmental pollution, they are expected to be alternative materials for polymer and conventional composite materials. This paper categorizes the requirements of magnesium alloys for several aerospace applications. Finally, the feasibility for applying the magnesium alloys to the space applications is discussed under their properties.