A method is provided for partially plating, for example, strip-shaped metallic straps which are parts of a support grid for a nuclear fuel assembly, and further relates to a masking jig for use in the method. The masking jig has a plurality of tubular bodies and a support plate on which the tubular bodies are fixed. A pair of slits is formed in each of the tubular bodies. When carrying out partial plating, a strap is inserted into the slits so that each of the portions of the strap not to be plated are arranged within each of the tubular bodies. By subsequently carrying out plating, a plating layer can be formed on the portions of the strap to be plated, without forming a plating layer on the portions of the strap not to be plated. Moreover, it is possible to prevent any damage from being inflicted to the portions not to be plated due to external force.