Process of masking cooling holes of a gas turbine component

[Solution means] In the method of masking the cooling hole (4) of a gas turbine component (1) which has an outer surface (6), a cave (2), and two or more cooling holes (4), This method each following stage to included; (a) outer surface (6) in the nearest portion, It is a cooling hole to the level of an outer surface (6) substantially. He is Ma to a cooling hole (4) so that (4) may be partially packed at least with mask material (5). スク material (5) is applied, In the portion traced by the outer surface (6) of the component (1) at least, mask material (5) contains the charge of a filler -- (b) -- at least -- the portion of the mask material (5a) inside a cooling hole (4) -- at least -- partial --, [thicken and] (c) The above-mentioned method characterized by removing the mask material (5a) which covered the outer surface (6) and the cooling hole (4) by which the mask was carried out of the component (1), and remains from (d) cooling hole (4), and which thickened.