To provide a method capable of estimating the life of a surface-treated steel material with high accuracy, a method for designing the surface-treated steel material, and a method for manufacturing the surface-treated steel material.

The method for estimating the life of the surface-treated steel material has a process (S21) for calculating the relation between an environmental factor and corrosion quantity on the basis of data showing the relation between the corrosion quantity and an exposure time under a plurality of actual environments and the environmental factor of the data, a process (S22) for determining a dominant environmental factor from the relation between the environmental factor and the corrosion quantity; a process (S23) for measuring the values of the dominant environmental factor in a plurality of regions of a target actual structure or a structure simulating the target actual structure, and a process (S24) for calculating the data showing the corrosion quantity and the exposure time of each of the regions on the basis of the relation between the environmental factor and the corrosion quantity and the measured values of the environmental factor and estimating the advance of corrosion on the basis of the data showing the relation between the corrosion quantity and the exposure time.