Provided is a flux-cored wire that is for build-up welding, can obtain a target welding metal composition by means of a low number of layers, and has a low base material dilution. The flux-cored wire for build-up welding, which is such that flux fills the inside of an outer skin, has a composition satisfying the belowmentioned formula (I) when, with respect to the total mass of the flux, the total content (F equivalent value) of alkali metal fluorides and alkaline earth metal fluorides is A (mass %), the total content of alkali metal elemental metals and alkaline earth metal elemental metals is B (mass %), and the total content of alkali metal oxides and alkaline earth metal oxides is C (mass %): 0.3≦[A/{1+0.7×(B+2C)}]≦2.0  (I).